Photopolymerizable compositions including a urethane component and a reactive diluent, articles, and methods

ABSTRACT

The present disclosure provides a photopolymerizable composition comprising 50-90 wt % of at least one urethane component, 5-50 wt % of at least one reactive diluent, 0.1-5 wt % of a photoinitiator, and optionally an inhibitor, wherein said composition has a viscosity at a temperature of 40 degrees Celsius of 10 Pa·s or less, as determined using a magnetic bearing rheometer using a 40 mm cone and plate measuring system at a shear rate of 0.1 l/s. The present disclosure also provides an article including the reaction product of the photopolymerizable composition, in which the article exhibits an elongation at break of 25% or greater. Further, the present disclosure provides a method of making an article including (i) providing a photopolymerizable composition and (ii) selectively curing the photopolymerizable composition to form an article. The method optionally also includes (iii) curing unpolymerized urethane component and/or reactive diluent remaining after step (ii). Further, methods are provided, including receiving, by a manufacturing device having one or more processors, a digital object comprising data specifying an article; and generating, with the manufacturing device by an additive manufacturing process, the article based on the digital object. A system is also provided, including a display that displays a 3D model of an article; and one or more processors that, in response to the 3D model selected by a user, cause a 3D printer to create a physical object of an article.

TECHNICAL FIELD

The present disclosure broadly relates to articles including a urethanecomponent and at least one reactive diluent, and methods of making thearticles, such as additive manufacturing methods.

BACKGROUND

The use of stereolithography and inkjet printing to producethree-dimensional articles has been known for a relatively long time,and these processes are generally known as methods of so called 3Dprinting (or additive manufacturing). In vat polymerization techniques(of which stereolithography is one type), the desired 3D article isbuilt up from a liquid, curable composition with the aid of a recurring,alternating sequence of two steps: in the first step, a layer of theliquid, curable composition, one boundary of which is the surface of thecomposition, is cured with the aid of appropriate radiation within asurface region which corresponds to the desired cross-sectional area ofthe shaped article to be formed, at the height of this layer, and in thesecond step, the cured layer is covered with a new layer of the liquid,curable composition, and the sequence of steps is repeated until aso-called green body (i.e., gelled article) of the desired shape isfinished. This green body is often not yet fully cured and must,usually, be subjected to post-curing. The mechanical strength of thegreen body immediately after curing, otherwise known as green strength,is relevant to further processing of the printed articles.

Other 3D printing techniques use inks that are jetted through a printhead as a liquid to form various three-dimensional articles. Inoperation, the print head may deposit curable photopolymers in alayer-by-layer fashion. Some jet printers deposit a polymer inconjunction with a support material or a bonding agent. In someinstances, the build material is solid at ambient temperatures andconverts to liquid at elevated jetting temperatures. In other instances,the build material is liquid at ambient temperatures.

One particularly attractive opportunity for 3D printing is in the directcreation of orthodontic clear tray aligners. These trays, also known asaligners or polymeric or shell appliances, are provided in a series andare intended to be worn in succession, over a period of months, in orderto gradually move the teeth in incremental steps towards a desiredtarget arrangement. Some types of clear tray aligners have a row oftooth-shaped receptacles for receiving each tooth of the patient'sdental arch, and the receptacles are oriented in slightly differentpositions from one appliance to the next in order to incrementally urgeeach tooth toward its desired target position by virtue of the resilientproperties of the polymeric material. A variety of methods have beenproposed in the past for manufacturing clear tray aligners and otherresilient appliances. Typically, positive dental arch models arefabricated for each dental arch using additive manufacturing methodssuch as stereolithography described above. Subsequently, a sheet ofpolymeric material is placed over each of the arch models and formedunder heat, pressure and/or vacuum to conform to the model teeth of eachmodel arch. The formed sheet is cleaned and trimmed as needed and theresulting arch-shaped appliance is shipped along with the desired numberof other appliances to the treating professional.

An aligner or other resilient appliance created directly by 3D printingwould eliminate the need to print a mold of the dental arch and furtherthermoform the appliance. It also would allow new aligner designs andgive more degrees of freedom in the treatment plan. Exemplary methods ofdirect printing clear tray aligners and other resilient orthodonticapparatuses are set forth in PCT Publication Nos. WO2016/109660 (Raby etal.), WO2016/148960 (Cinader et al.), and WO2016/149007 (Oda et al.) aswell as US Publication Nos. US2011/0091832 (Kim, et al.) andUS2013/0095446 (Kitching).

SUMMARY

Existing printable/polymerizable resins tend to be too brittle (e.g.,low elongation, short-chain crosslinked bonds, thermoset composition,and/or high glass transition temperature) for a resilient oral appliancesuch as an aligner. An aligner or other appliance prepared from suchresins could easily break in the patient's mouth during treatment,creating material fragments that may abrade or puncture exposed tissueor be swallowed. These fractures at the very least interrupt treatmentand could have serious health consequences for the patient. Thus, thereis a need for curable liquid resin compositions that are tailored andwell suited for creation of resilient articles using 3D printing (e.g.,additive manufacturing) method. Preferably, curable liquid resincompositions to be used in the vat polymerization 3D printing processhave low viscosity, a proper curing rate, and excellent mechanicalproperties in both the final cured article. In contrast, compositionsfor inkjet printing processes need to be much lower viscosity to be ableto jetted through nozzles, which is not the case for most vatpolymerization resins.

Urethane (meth)acrylates are a class of raw materials that haveinteresting properties, for example an elongation of over 100% whencured, and very high toughness. But these resins also have a very highviscosity; at room temperature they are basically solids. Therefore,they only have been used in small amounts in photosensitive resinformulations for vat polymerization or stereolithography, and theproperties of these resins are dominated by the other components.

In a first aspect, a photopolymerizable composition is provided. Thephotopolymerizable composition includes (a) 50 to 90 wt. %, inclusive,of at least one urethane component and (b) 5 to 50 wt. %, inclusive, ofat least one reactive diluent. The photopolymerizable compositionfurther includes (c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and(d) an optional inhibitor in an amount of 0.001 to 1 wt. %, inclusive,if present; based on the total weight of the photopolymerizablecomposition. Often, the photopolymerizable composition has a viscosityat a temperature of 40 degrees Celsius of 10 Pa·s or less, as determinedusing a magnetic bearing rheometer using a 40 mm cone and platemeasuring system at a shear rate of 0.1 l/s.

In a second aspect, an article is provided. The article includes areaction product of a photopolymerizable composition including (a) 50 to90 wt. %, inclusive, of at least one urethane component and (b) 5 to 50wt. %, inclusive, of at least one reactive diluent. Thephotopolymerizable composition further includes (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition. Typically, the articleexhibits an elongation at break of 25% or greater.

In a third aspect, a method of making an article is provided. The methodincludes (i) providing a photopolymerizable composition and (ii)selectively curing the photopolymerizable composition to form anarticle. The method optionally also includes (iii) curing unpolymerizedurethane component and/or reactive diluent remaining after step (ii).The photopolymerizable composition includes (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition;

In a fourth aspect, a non-transitory machine readable medium isprovided. The non-transitory machine readable medium has datarepresenting a three-dimensional model of an article, when accessed byone or more processors interfacing with a 3D printer, causes the 3Dprinter to create an article. The article includes a reaction product ofa photopolymerizable composition including (a) 50 to 90 wt. %,inclusive, of at least one urethane component and (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent. The photopolymerizablecomposition further includes (c) 0.1 to 5 wt. %, inclusive, of aphotoinitiator and (d) an optional inhibitor in an amount of 0.001 to 1wt. %, inclusive, if present; based on the total weight of thephotopolymerizable composition. The article exhibits an elongation atbreak of 25% or greater.

In a fifth aspect, a method is provided. The method includes retrieving,from a non-transitory machine readable medium, data representing a 3Dmodel of an article; executing, by one or more processors, a 3D printingapplication interfacing with a manufacturing device using the data; andgenerating, by the manufacturing device, a physical object of thearticle. The article includes a reaction product of a photopolymerizablecomposition including (a) 50 to 90 wt. %, inclusive, of at least oneurethane component and (b) 5 to 50 wt. %, inclusive, of at least onereactive diluent. The photopolymerizable composition further includes(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition. The articleexhibits an elongation at break of 25% or greater.

In a sixth aspect, another method is provided. The method includesreceiving, by a manufacturing device having one or more processors, adigital object comprising data specifying a plurality of layers of anarticle; and generating, with the manufacturing device by an additivemanufacturing process, the article based on the digital object. Thearticle includes a reaction product of a photopolymerizable compositionincluding (a) 50 to 90 wt. %, inclusive, of at least one urethanecomponent and (b) 5 to 50 wt. %, inclusive, of at least one reactivediluent. The photopolymerizable composition further includes (c) 0.1 to5 wt. %, inclusive, of a photoinitiator and (d) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition. The article exhibits anelongation at break of 25% or greater.

In a seventh aspect, a system is provided. The system includes a displaythat displays a 3D model of an article; and one or more processors that,in response to the 3D model selected by a user, cause a 3D printer tocreate a physical object of an article. The article includes a reactionproduct of a photopolymerizable composition including (a) 50 to 90 wt.%, inclusive, of at least one urethane component and (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent. The photopolymerizablecomposition further includes (c) 0.1 to 5 wt. %, inclusive, of aphotoinitiator and (d) an optional inhibitor in an amount of 0.001 to 1wt. %, inclusive, if present; based on the total weight of thephotopolymerizable composition. The article exhibits an elongation atbreak of 25% or greater.

Clear tray aligners and tensile bars made according to at least certainembodiments of this disclosure were found to show low brittleness, goodresistance to water, and good toughness.

The above summary of the present disclosure is not intended to describeeach disclosed embodiment or every implementation of the presentdisclosure. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a process for building an article using thephotopolymerizable compositions disclosed herein.

FIG. 2 is a generalized schematic of a stereolithography apparatus.

FIG. 3 is an isometric view of a printed clear tray aligner, accordingto one embodiment of the present disclosure.

FIG. 4 is a flowchart of a process for manufacturing a printedorthodontic appliance according to the present disclosure.

FIG. 5 is a generalized schematic of an apparatus in which radiation isdirected through a container.

FIG. 6 is a block diagram of a generalized system 600 for additivemanufacturing of an article.

FIG. 7 is a block diagram of a generalized manufacturing process for anarticle.

FIG. 8 is a high-level flow chart of an exemplary article manufacturingprocess.

FIG. 9 is a high-level flow chart of an exemplary article additivemanufacturing process.

FIG. 10 is a schematic front view of an exemplary computing device 1000.

While the above-identified figures set forth several embodiments of thedisclosure other embodiments are also contemplated, as noted in thedescription. The figures are not necessary drawn to scale. In all cases,this disclosure presents the invention by way of representation and notlimitation. It should be understood that numerous other modificationsand embodiments can be devised by those skilled in the art, which fallwithin the scope and spirit of the principles of the invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As used herein, the terms “hardenable” refers to a material that can becured or solidified, e.g., by heating to remove solvent, heating tocause polymerization, chemical crosslinking, radiation-inducedpolymerization or crosslinking, or the like.

As used herein, “curing” means the hardening or partial hardening of acomposition by any mechanism, e.g., by heat, light, radiation, e-beam,microwave, chemical reaction, or combinations thereof.

As used herein, “cured” refers to a material or composition that hasbeen hardened or partially hardened (e.g., polymerized or crosslinked)by curing.

As used herein, “integral” refers to being made at the same time orbeing incapable of being separated without damaging one or more of the(integral) parts.

As used herein, the term “(meth)acrylate” is a shorthand reference toacrylate, methacrylate, or combinations thereof, and “(meth)acrylic” isa shorthand reference to acrylic, methacrylic, or combinations thereof.As used herein, “(meth)acrylate-functional compounds” are compounds thatinclude, among other things, a (meth)acrylate moiety.

As used herein, “non-crosslinkable” refers to a polymer that does notundergo crosslinking when exposed to actinic radiation or elevated heat.Typically, non-crosslinkable polymers are non-functionalized polymerssuch that they lack functional groups that would participate incrosslinking.

As used herein, “oligomer” refers to a molecule that has one or moreproperties that change upon the addition of a single further repeatunit.

As used herein, “polymer” refers to a molecule having one or moreproperties that do not change upon the addition of a single furtherrepeat unit.

As used herein, “polymerizable composition” means a hardenablecomposition that can undergo polymerization upon initiation (e.g.,free-radical polymerization initiation). Typically, prior topolymerization (e.g., hardening), the polymerizable composition has aviscosity profile consistent with the requirements and parameters of oneor more 3D printing systems. In some embodiments, for instance,hardening comprises irradiating with actinic radiation having sufficientenergy to initiate a polymerization or cross-linking reaction. Forinstance, in some embodiments, ultraviolet (UV) radiation, e-beamradiation, or both, can be used.

As used herein, a “resin” contains all polymerizable components(monomers, oligomers and/or polymers) being present in a hardenablecomposition. The resin may contain only one polymerizable componentcompound or a mixture of different polymerizable compounds.

As used herein, “thermoplastic” refers to a polymer that flows whenheated sufficiently above its glass transition point and become solidwhen cooled.

As used herein, “thermoset” refers to a polymer that permanently setsupon curing and does not flow upon subsequent heating. Thermosetpolymers are typically crosslinked polymers.

As used herein, “occlusal” means in a direction toward the outer tips ofthe patient's teeth; “facial” means in a direction toward the patient'slips or cheeks; and “lingual” means in a direction toward the patient'stongue.

The words “preferred” and “preferably” refer to embodiments of thedisclosure that may afford certain benefits, under certaincircumstances. However, other embodiments may also be preferred, underthe same or other circumstances. Furthermore, the recitation of one ormore preferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the disclosure.

In this application, terms such as “a”, “an”, and “the” are not intendedto refer to only a singular entity, but include the general class ofwhich a specific example may be used for illustration. The terms “a”,“an”, and “the” are used interchangeably with the term “at least one.”

The phrases “at least one of” and “comprises at least one of” followedby a list refers to any one of the items in the list and any combinationof two or more items in the list.

As used herein, the term “or” is generally employed in its usual senseincluding “and/or” unless the content clearly dictates otherwise.

The term “and/or” means one or all of the listed elements or acombination of any two or more of the listed elements.

Also herein, all numbers are assumed to be modified by the term “about”and preferably by the term “exactly.” As used herein in connection witha measured quantity, the term “about” refers to that variation in themeasured quantity as would be expected by the skilled artisan making themeasurement and exercising a level of care commensurate with theobjective of the measurement and the precision of the measuringequipment used. Also herein, the recitations of numerical ranges byendpoints include all numbers subsumed within that range as well as theendpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

As used herein as a modifier to a property or attribute, the term“generally”, unless otherwise specifically defined, means that theproperty or attribute would be readily recognizable by a person ofordinary skill but without requiring absolute precision or a perfectmatch (e.g., within +/−20% for quantifiable properties). The term“substantially”, unless otherwise specifically defined, means to a highdegree of approximation (e.g., within +/−10% for quantifiableproperties) but again without requiring absolute precision or a perfectmatch. Terms such as same, equal, uniform, constant, strictly, and thelike, are understood to be within the usual tolerances or measuringerror applicable to the particular circumstance rather than requiringabsolute precision or a perfect match.

In a first aspect, the present disclosure provides a photopolymerizablecomposition. The photopolymerizable composition comprises:

(a) 50 to 90 wt. %, inclusive, of at least one urethane component;

(b) 5 to 50 wt. %, inclusive, of at least one reactive diluent;

(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and

(d) an optional inhibitor in an amount of 0.001 to 1 wt. %, inclusive,if present; based on the total weight of the photopolymerizablecomposition. The components (a) through (d) are discussed in detailbelow.

Urethane Component

The photopolymerizable compositions of the present disclosure include atleast one urethane component. As used herein, a “urethane component”refers to a compound including one or more carbamate functionalities inthe backbone of the compound. In certain embodiments, the carbamatefunctionality is of Formula I:

—N(H)—C(O)O—  I.

Urethanes are prepared by the reaction of an isocyanate with an alcoholto form carbamate linkages. Moreover, the term “polyurethane” has beenused more generically to refer to the reaction products ofpolyisocyanates with any polyactive hydrogen compound includingpolyfunctional alcohols, amines, and mercaptans.

The at least one urethane component provides both toughness (e.g., atleast a minimum tensile strength and/or modulus) and flexibility (e.g.,at least a minimum elongation at break) to the final article. In someembodiments, in addition to the urethane functionality, the urethanecomponent further comprises one or more functional groups selected fromhydroxyl groups, carboxyl groups, amino groups, and siloxane groups.These functional groups can be reactive with other components of thephotopolymerizable composition during polymerization. The at least oneurethane component often comprises a urethane (meth)acrylate, a urethaneacrylamide, or combinations thereof, and wherein the at least oneurethane component comprises a linking group selected from alkyl,polyalkylene, polyalkylene oxide, aryl, polycarbonate, polyester,polyamide, and combinations thereof. As used herein, “linking group”refers to a functional group that connects two or more urethane groups.The linking group may be divalent, trivalent, or tetravalent. In selectembodiments, the at least one urethane component comprises a urethane(meth)acrylate comprising a polyalkylene oxide linking group, apolyamide linking group, or combinations thereof.

For example, the polymerizable component can include polyfunctionalurethane acrylates or urethane methacrylates. These urethane(meth)acrylates are known to the person skilled in the art and can beprepared in a known manner by, for example, reacting ahydroxyl-terminated polyurethane with acrylic acid, methacrylic acid, orisocyanatoethyl methacrylate, or by reacting an isocyanate-terminatedprepolymer with hydroxyalkyl (meth)acrylates to give the urethane(meth)acrylate. Suitable processes are disclosed, inter alia, in U.S.Pat. No. 8,329,776 (Hecht et al.) and U.S. Pat. No. 9,295,617 (Cub etal.). Suitable urethane methacrylates can include PEGDMA(polyethyleneglycol dimethacrylate having a molecular weight ofapproximately 400), aliphatic urethane methacrylates, aliphaticpolyester urethane methacrylates, and aliphatic polyester triurethaneacrylates.

Typically, the urethane component comprises a number average molecularweight (Mn) of 200 grams per mole to 5,000 grams per mole. The numberaverage molecular weight may be measured by matrix assisted laserdeposition ionization mass spectrometry (MALDI). The “urethanecomponent” as used herein optionally includes each of a “high Mnurethane component” and a “low Mn urethane component”. The high Mnurethane component encompasses compounds including one or more urethanefunctionalities in the backbone of the compound and that have a numberaverage molecular weight of 1,000 grams per mole (g/mol) or greater,with the proviso that all branches off the backbone of the compound, ifpresent, have a Mn of no more than 200 g/mol. Stated another way, thehigh Mn urethane component typically has a Mn of 1,000 g/mol or greater,1,100 g/mol or greater, 1,200 g/mol or greater, 1,300 g/mol or greater,1,400 g/mol or greater, 1,500 g/mol or greater, 1,600 g/mol or greater,1,700 g/mol or greater, 1,800 g/mol or greater, 2,000 g/mol or greater,2,250 g/mol or greater, 2,500 g/mol or greater, 2,750 g/mol or greater,3,000 g/mol or greater, 3,250 g/mol or greater, 3,500 g/mol or greater,3,7500 g/mol or greater, or even 4,000 g/mol or greater; and 5,000 g/molor less, 4,800 g/mol or less, 4,600 g/mol or less, 4,400 g/mol or less,4,100 g/mol or less, 3,900 g/mol or less, 3,700 g/mol or less, 3,400g/mol or less, 3,100 g/mol or less, 2,900 g/mol or less, 2,700 g/mol orless, 2,400 g/mol or less, or 2,200 g/mol or less, or even 1,900 g/molor less.

The low Mn urethane component encompasses compounds including one ormore urethane functionalities in the backbone of the compound and thathave either 1) a number average molecular weight of 100 g/mol or greaterand up to but not including 1,000 g/mol, or 2) a number averagemolecular weight of 100 g/mol or greater and 2,000 g/mol or less, withthe proviso that a number average molecular weight of any one or morelinear portions between two reactive groups and/or branches is up to butnot including 1,000 g/mol. For instance, a branched urethane componentcan have a total Mn of greater than 1,000 g/mol but still be a low Mnurethane component due to having a linear segment between two branchingpoints with a Mn of less than 1,000 g/mol. Stated another way, the 1)category of low Mn urethane components typically have a Mn of 100 g/molor greater, 150 g/mol or greater, 200 g/mol or greater, 250 g/mol orgreater, 300 g/mol or greater, 350 g/mol or greater, 400 g/mol orgreater, 450 g/mol or greater, 500 g/mol or greater, 550 g/mol orgreater, 600 g/mol or greater, 650 g/mol or greater, 700 g/mol orgreater, 750 g/mol or greater, or 800 g/mol or greater; and up to butnot including 1,000 g/mol, 975 g/mol or less, 925 g/mol or less, 875g/mol or less, 825 g/mol or less, 775 g/mol or less, 725 g/mol or less,675 g/mol or less, 625 g/mol or less, 575 g/mol or less, 525 g/mol orless, 475 g/mol or less, or 425 g/mol or less, or even 375 g/mol orless. The 2) category of low Mn urethane components typically have a Mnof 200 g/mol or greater, 250 g/mol or greater, 300 g/mol or greater, 350g/mol or greater, 400 g/mol or greater, 450 g/mol or greater, 500 g/molor greater, 550 g/mol or greater, 600 g/mol or greater, 650 g/mol orgreater, 700 g/mol or greater, 750 g/mol or greater, or 800 g/mol orgreater; and 1,500 g/mol or less, 1,400 g/mol or less, 1,300 g/mol orless, 1,200 g/mol or less, 1,100 g/mol or less, 1,000 g/mol or less, 975g/mol or less, 925 g/mol or less, 875 g/mol or less, 825 g/mol or less,775 g/mol or less, 725 g/mol or less, 675 g/mol or less, 625 g/mol orless, 575 g/mol or less, 525 g/mol or less, 475 g/mol or less, or 425g/mol or less, or even 375 g/mol or less. Each of the foregoing secondcategory of low Mn urethane components includes the proviso that anumber average molecular weight of any one or more linear portionsbetween two reactive groups and/or branches is up to but not including1,000 g/mol, 950 g/mol or less, 900 g/mol or less, 850 g/mol or less,800 g/mol or less, or 750 g/mol or less; and a number average molecularweight of any one or more linear portions between two reactive groupsand/or branches is 100 g/mol or greater, 200 g/mol or greater, 250 g/molor greater, 300 g/mol or greater, 350 g/mol or greater, 400 g/mol orgreater, 450 g/mol or greater, or 500 g/mol or greater.

The use of high Mn urethane components having a number average molecularweight of 1,000 g/mol or greater tend to provide a final article havingat least a certain desirable minimum elongation at break (e.g., 25% orgreater). Eighty percent by weight or greater of the at least oneurethane component is provided by one or more high Mn (e.g., long chain)urethane components. More particularly, in embodiments where a lowmolecular weight urethane component is present, typical ratios of thehigh number average molecular weight urethane component to the lownumber average molecular weight urethane component range from 95:5 highMn urethane component to low Mn urethane component to 80:20 high Mnurethane component to low Mn urethane component. Stated another way,photopolymerizable compositions according to at least certain aspects ofthe disclosure include 80 wt. % or more of the total urethane componentas a high Mn urethane component, 85 wt. % or more, 87 wt. % or more, 90wt. % or more, 92 wt. % or more, 95 wt. % or more, or even 97 wt. % ormore of the total urethane component as a high Mn urethane component;and 100% or less of the total urethane component as a high Mn urethanecomponent, 98 wt. % or less, 96 wt. % or less, 94 wt. % or less, 91 wt.% or less, 89 wt. % or less, or 86 wt. % or less of the total urethanecomponent as a high Mn urethane component. Similarly, photopolymerizablecompositions according to at least certain aspects of the disclosure caninclude 2 wt. % or more of the total urethane component as a low Mnurethane component, 4 wt. % or more, 5 wt. % or more, 8 wt. % or more,10 wt. % or more, 12 wt. % or more, 15 wt. % or more, or even 17 wt. %or more of the total urethane component as a low Mn urethane component;and 20 wt. % or less of the total urethane component as a low Mnurethane component, 18 wt. % or less, 16 wt. % or less, 14 wt. % orless, 11 wt. % or less, 9 wt. % or less, 7 wt. % or less, 6 wt. % orless, or 3 wt. % or less of the total urethane component as a low Mnurethane component.

According to certain embodiments, at least one urethane componentcomprises at least one (meth)acrylate component having a urethanemoiety, which may help to improve physical properties of the curedcomposition like flexural strength and/or elongation at break. Such aurethane component can be characterized by the following features aloneor in combination:

a) comprising at least 2 or 3 or 4 (meth)acrylate moieties;

b) number average molecular weight (Mn): from 1,000 to 5,000 g/mol orfrom 1,000 to 2000 g/mol;

c) comprising a C1 to C20 linear or branched alkyl moiety to which the(meth)acrylate moieties are attached through urethane moieties;

d) viscosity: from 0.1 to 100 Pa·s or 1 to 50 Pa·s at 23° C.

A combination of the features a) and b) or b) and c) or a) and d) cansometimes be preferred.

Urethane (meth)acrylates may be obtained by a number of processes knownto the skilled person. The urethane(meth)acrylates are typicallyobtained by reacting an NCO-terminated compound with a suitablemonofunctional (meth)acrylate monomer such as hydroxyethyl acrylate,hydroxyethyl methacrylate, hydroxypropylmethacrylate, preferablyhydroxyethyl- and hydroxypropylmethacrylate. For example, apolyisocyanate and a polyol may be reacted to form anisocyanate-terminated urethane prepolymer that is subsequently reactedwith a (meth)acrylate such as 2-hydroxy ethyl(meth)acrylate. These typesof reactions may be conducted at room temperature or higher temperature,optionally in the presence of catalysts such as tin catalysts, tertiaryamines and the like.

Polyisocyanates which can be employed to form isocyanate-functionalurethane prepolymers can be any organic isocyanate having at least twofree isocyanate groups. Included are aliphatic cycloaliphatic, aromaticand araliphatic isocyanates. Any of the known polyisocyanates such asalkyl and alkylene polyisocyanates, cycloalkyl and cycloalkylenepolyisocyanates, and combinations such as alkylene and cycloalkylenepolyisocyanates can be employed. Preferably, diisocyanates having theformula X(NCO)₂ can be used, with X representing an aliphatichydrocarbon radical with 2 to 12 C atoms, a cycloaliphatic hydrocarbonradical with 5 to 18 C atoms, an aromatic hydrocarbon radical with 6 to16 C atoms and/or an aliphatic hydrocarbon radical with 7 to 15 C atoms.

Examples of suitable polyisocyanates include2,2,4-trimethylhexamethylene-1,6-diisocyanate,hexamethylene-1,6-diisocyanate (HDI), cyclohexyl-1,4-diisocyanate,4,4′-methylene-bis(cyclohexyl isocyanate),1,1′-methylenebis(4-isocyanato) cyclohexane, isophorone diisocyanate,4,4′-methylene diphenyl diisocyanate, 1,4-tetramethylene diisocycanate,meta- and para-tetra¬methylxylene diisocycanate, 1,4-phenylenediisocycanate, 2,6- and 2,4-toluene diisocycanate, 1,5-naphthylenediisocycanate, 2,4′ and 4,4′-diphenylmethane diisocycanate and mixturesthereof.

It is also possible to use higher-functional polyisocyanates known frompolyurethane chemistry or else modified polyisocyanates, for examplecontaining carbodiimide groups, allophanate groups, isocyanurate groupsand/or biuret groups. Particularly preferred isocyanates are isophoronediisocyanate, 2,4,4-trimethyl-hexamethylene diisocyanate andhigher-functional polyisocyanates with isocyanurate structure.

The isocyanate terminated urethane compound is capped with a(meth)acrylate to produce a urethane(meth)acrylate compound. In general,any (meth)acrylate-type capping agent having a terminal hydroxyl groupand also having an acrylic or methacrylic moiety can be employed, withthe methacrylic moiety being preferred. Examples of suitable cappingagents include 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, glycerol di(meth)acrylate and/or trimethylolpropanedi(meth)acrylate. Particularly preferred are 2-hydroxyethyl methacrylate(HEMA) and/or 2-hydroxyethyl acrylate (HEA).

The equivalence ratio of isocyanate groups to compounds reactivevis-à-vis isocyanate groups is 1.1:1 to 8:1, preferably 1.5:1 to 4:1.

The isocyanate polyaddition reaction can take place in the presence ofcatalysts known from polyurethane chemistry, for example organotincompounds such as dibutyltin dilaurate or amine catalysts such asdiazabicyclo[2.2.2]octane. Furthermore, the synthesis can take placeboth in the melt or in a suitable solvent which can be added before orduring the prepolymer preparation. Suitable solvents are for exampleacetone, 2-butanone, tetrahydrofurane, dioxane, dimethylformamide,N-methyl-2-pyrrolidone (NMP), ethyl acetate, alkyl ethers of ethyleneand propylene glycol and aromatic hydrocarbons. The use of ethyl acetateas solvent is particularly preferred.

According to select embodiments the urethane dimethacrylate of thefollowing Formulas I and II are preferred:

wherein n=9 or 10;

Examples of commercially available urethane components include thoseavailable under the trade designations of EXOTHANE 108 (e.g., FormulaI), EXOTHANE 8, and EXOTHANE 10 (e.g., Formula II) from Esstech Inc, andDESMA from 3M Company. DESMA is described in, e.g., paragraph [0135] andTable 3 of EP2167013B1 (Hecht et al.).

The urethane component is included in the photopolymerizable compositionin an amount of 50 to 90 wt. %, inclusive, based on the total weight ofthe photopolymerizable composition, such as 60 to 80 wt. %, inclusive.Typically, the urethane component is included in the photopolymerizablecomposition in an amount of 50 wt. % or more, 52 wt. % or more, 55 wt. %or more, 57 wt. % or more, 60 wt. % or more, 61 wt. % or more, 62 wt. %or more, 63 wt. % or more, 64 wt. % or more, 65 wt. % or more, 70 wt. %or more, or 72 wt % or more; and 90 wt. % or less, 87 wt. % or less, 85wt. % or less, 80 wt. % or less, 77 wt. % or less, or 75 wt. % or less,based on the total weight of the photopolymerizable composition.

Reactive Diluent

The photopolymerizable compositions of the present disclosure include atleast one reactive diluent. A “reactive diluent,” for reference purposesherein, is a component that contains at least one free radicallyreactive group (e.g., an ethylenically-unsaturated group) that canco-react with the at least one urethane component (e.g., is capable ofundergoing addition polymerization). The reactive diluent has a smallermolecular weight than at least one (e.g., high Mn) urethane component,often less than 400 grams per mole, and does not contain any urethanefunctional groups (e.g., is free of any urethane functional groups).

In select embodiments, the at least one reactive diluent comprises a(meth)acrylate, a polyalkylene oxide di(meth)acrylate, an alkane dioldi(meth)acrylate, or combinations thereof, such as a (meth)acrylate.

Suitable free-radically polymerizable reactant diluents include di-,tri-, or other poly-acrylates and methacrylates such as glyceroldiacrylate, ethoxylated bisphenol A dimethacrylate (D-zethacrylate),tetraethylene glycol dimethacrylate (TEGDMA), glycerol triacrylate,ethyleneglycol diacrylate, diethyleneglycol diacrylate,triethyleneglycol dimethacrylate, 1,3-propanediol diacrylate,1,3-propanediol dimethacrylate, trimethylolpropane triacrylate,1,2,4-butanetriol trimethacrylate, 1,4-cyclohexanediol diacrylate,pentaerythritol triacrylate, pentaerythritol tetraacrylate,pentaerythritol tetramethacrylate, sorbitol hexacrylate,bis[1-(2-acryloxy)]-p-ethoxyphenyldimethylme thane, bis[1-(3-acryloxy-2-hydroxy)]-p-propoxyphenyl-dimethylmethane, andtrishydroxyethyl-isocyanurate trimethacrylate; the bis-acrylates andbis-methacrylates of polyethylene glycols of molecular weight 200-500,copolymerizable mixtures of acrylated monomers such as those in U.S.Pat. No. 4,652,274 (Boettcher et al.), and acrylated oligomers such asthose of U.S. Pat. No. 4,642,126 (Zador et al.); polyfunctional(meth)acrylates comprising urea or amide groups, such as those ofEP2008636 (Hecht et al.).

The reactive diluent can comprise one or more poly(meth)acrylates, forexample, di-, tri-, tetra- or pentafunctional monomeric or oligomericaliphatic, cycloaliphatic or aromatic acrylates or methacrylates.

Examples of suitable aliphatic poly(meth)acrylates having more than two(meth)acrylate groups in their molecules are the triacrylates andtrimethacrylates of hexane-2,4,6-triol; glycerol or1,1,1-trimethylolpropane; ethoxylated or propoxylated glycerol or1,1,1-trimethylolpropane; and the hydroxyl-containing tri(meth)acrylateswhich are obtained by reacting triepoxide compounds, for example thetriglycidyl ethers of said triols, with (meth)acrylic acid. It is alsopossible to use, for example, pentaerythritol tetraacrylate,bistrimethylolpropane tetraacrylate, pentaerythritolmonohydroxytriacrylate or -methacrylate, or dipentaerythritolmonohydroxypentaacrylate or -methacrylate.

Another suitable class of free radical polymerizable compounds includesaromatic di(meth)acrylate compounds and trifunctional or higherfunctionality (meth)acrylate compound.

Trifunctional or higher functionality meth(acrylates) can be tri-,tetra- or pentafunctional monomeric or oligomeric aliphatic,cycloaliphatic or aromatic acrylates or methacrylates.

Examples of suitable aliphatic tri-, tetra- and pentafunctional(meth)acrylates are the triacrylates and trimethacrylates ofhexane-2,4,6-triol; glycerol or 1,1,1-trimethylolpropane; ethoxylated orpropoxylated glycerol or 1,1,1-trimethylolpropane; and thehydroxyl-containing tri(meth)acrylates which are obtained by reactingtriepoxide compounds, for example the triglycidyl ethers of said triols,with (meth)acrylic acid. It is also possible to use, for example,pentaerythritol tetraacrylate, bistrimethylolpropane tetraacrylate,pentaerythritol monohydroxytriacrylate or -methacrylate, ordipentaerythritol monohydroxypentaacrylate or -methacrylate. In someembodiments, tri(meth)acrylates comprise 1,1-trimethylolpropanetriacrylate or methacrylate, ethoxylated or propoxylated1,1,1-trimethylolpropanetriacrylate or methacrylate, ethoxylated orpropoxylated glycerol triacrylate, pentaerythritol monohydroxytriacrylate or methacrylate, or tris(2-hydroxy ethyl) isocyanuratetriacrylate. Further examples of suitable aromatic tri(meth)acrylatesare the reaction products of triglycidyl ethers of trihydroxy benzeneand phenol or cresol novolaks containing three hydroxyl groups, with(meth)acrylic acid.

In some cases, a reactive diluent comprises diacrylate and/ordimethacrylate esters of aliphatic, cycloaliphatic or aromatic diols,including 1,3- or 1,4-butanediol, neopentyl glycol, 1,6-hexanediol,diethylene glycol, triethylene glycol, tetraethylene glycol,polyethylene glycol, tripropylene glycol, ethoxylated or propoxylatedneopentyl glycol, 1,4-dihydroxymethylcyclohexane,2,2-bis(4-hydroxycyclohexyl)propane or bis(4-hydroxycyclohexyl)methane,hydroquinone, 4,4′-dihydroxybiphenyl, bisphenol A, bisphenol F,bisphenol S, ethoxylated or propoxylated bisphenol A, ethoxylated orpropoxylated bisphenol F or ethoxylated or propoxylated bisphenol S. Insome cases, a reactive diluent described herein comprises one or morehigher functional acrylates or methacrylates such as dipentaerythritolmonohydroxy pentaacrylate or bis(trimethylolpropane)tetraacrylate.

In certain embodiments, the photopolymerizable composition consistsessentially of multifunctional components or is free of monofunctionalcomponents. This means that the photopolymerizable composition contains2 wt. % or less of monofunctional components. An advantage of suchphotopolymerizable compositions is that they tend to contain a minimalto zero amount of unreacted reactive diluent that is capable of leachingout of an article following cure. For applications in which the articleis an orthodontic article, this minimizes release of unreacted reactivediluent into a patient's mouth.

In certain embodiments, the at least one reactive diluent has amolecular weight of 400 grams per mole or less, 375 g/mol or less, 350g/mol or less, 325 g/mol or less, 300 g/mol or less, 275 g/mol or less,225 g/mol or less, or 200 g/mol or less. Including one or more reactivediluents with such molecular weights can assist in providing aphotopolymerizable composition that has a sufficiently low viscosity foruse with vat polymerization methods. In certain embodiments, the atleast one reactive diluent comprises a molecular weight of 200 g/mol to400 g/mol, inclusive.

The reactive diluent is included in the photopolymerizable compositionin an amount of 5 to 50 wt. %, inclusive, based on the total weight ofthe photopolymerizable composition, such as 25 to 50 wt. %, inclusive.Typically, the reactive diluent is included in the photopolymerizablecomposition in an amount of 5 wt. % or more, 10 wt. % or more, 15 wt. %or more, 20 wt. % or more, 25 wt. % or more, or 30 wt. % or more; and 50wt. % or less, 45 wt. % or less, 40 wt. % or less, 35 wt. % or less, 30wt. % or less, 25 wt. % or less, or 20 wt. % or less, based on the totalweight of the photopolymerizable composition.

Additives

Photopolymerizable compositions described herein, in some instances,further comprise one or more additives, such as one or more additivesselected from the group consisting of photoinitiators, inhibitors,stabilizing agents, sensitizers, absorption modifiers, fillers andcombinations thereof. For example, the photopolymerizable compositionfurther comprises one or more photoinitiators. Suitable exemplaryphotoinitiators are those available under the trade designationsIRGACURE and DAROCUR from BASF (Ludwigshafen, Germany) and include1-hydroxycyclohexyl phenyl ketone (IRGACURE 184),2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651), bis(2,4,6trimethylbenzoyl)phenylphosphineoxide (IRGACURE 819),1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone(IRGACURE 369),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE907), Oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone]ESACURE ONE (Lamberti S.p.A., Gallarate, Italy),2-hydroxy-2-methyl-1-phenyl propan-1-one (DAROCUR 1173), 2, 4,6-trimethylbenzoyldiphenylphosphine oxide (IRGACURE TPO), and 2, 4,6-trimethylbenzoylphenyl phosphinate (IRGACURE TPO-L). Additionalsuitable photoinitiators include for example and without limitation,benzyl dimethyl ketal, 2-methyl-2-hydroxypropiophenone, benzoin methylether, benzoin isopropyl ether, anisoin methyl ether, aromatic sulfonylchlorides, photoactive oximes, and combinations thereof.

A photoinitiator can be present in a photopolymerizable compositiondescribed herein in any amount according to the particular constraintsof the additive manufacturing process. In some embodiments, aphotoinitiator is present in a photopolymerizable composition in anamount of up to about 5% by weight, based on the total weight of thephotopolymerizable composition. In some cases, a photoinitiator ispresent in an amount of about 0.1-5% by weight, based on the totalweight of the photopolymerizable composition.

In addition, a photopolymerizable material composition described hereincan further comprise one or more sensitizers to increase theeffectiveness of one or more photoinitiators that may also be present.In some embodiments, a sensitizer comprises isopropylthioxanthone (ITX)or 2-chlorothioxanthone (CTX). Other sensitizers may also be used. Ifused in the photopolymerizable composition, a sensitizer can be presentin an amount ranging of about 0.01% by weight or about 1% by weight,based on the total weight of the photopolymerizable composition.

A photopolymerizable composition described herein optionally alsocomprises one or more polymerization inhibitors or stabilizing agents. Apolymerization inhibitor is often included in a photopolymerizablecomposition to provide additional thermal stability to the composition.A stabilizing agent, in some instances, comprises one or moreanti-oxidants. Any anti-oxidant not inconsistent with the objectives ofthe present disclosure may be used. In some embodiments, for example,suitable anti-oxidants include various aryl compounds, includingbutylated hydroxytoluene (BHT), which can also be used as apolymerization inhibitor in embodiments described herein. In addition toor as an alternative, a polymerization inhibitor comprisesmethoxyhydroquinone (MEHQ).

In some embodiments, a polymerization inhibitor, if used, is present inan amount of about 0.001-2% by weight, 0.001 to 1% by weight, or 0.01-1%by weight, based on the total weight of the photopolymerizablecomposition. Further, if used, a stabilizing agent is present in aphotopolymerizable composition described herein in an amount of about0.1-5% by weight, about 0.5-4% by weight, or about 1-3% by weight, basedon the total weight of the photopolymerizable composition.

A photopolymerizable composition as described herein can also compriseone or more absorption modifiers (e.g., dyes, optical brighteners,pigments, particulate fillers, etc.) to control the penetration depth ofactinic radiation. One particularly suitable absorption modifier isTinopal OB, a benzoxazole,2,2′-(2,5-thiophenediyl)bis[5-(1,1-dimethylethyl)], available from BASFCorporation, Florham Park, N.J. The absorption modifier, if used, can bepresent in an amount of about 0.001-5% by weight, about 0.01-1% byweight, about 0.1-3% by weight, or about 0.1-1% by weight, based on thetotal weight of the photopolymerizable composition.

Photopolymerizable compositions may include fillers, includingnano-scale fillers. Examples of suitable fillers are naturally occurringor synthetic materials including, but not limited to: silica (SiO₂(e.g., quartz)); alumina (Al₂O₃), zirconia, nitrides (e.g., siliconnitride); glasses and fillers derived from, for example, Zr, Sr, Ce, Sb,Sn, Ba, Zn, and Al; feldspar; borosilicate glass; kaolin (china clay);talc; zirconia; titania; and submicron silica particles (e.g., pyrogenicsilicas such as those available under the trade designations AEROSIL,including “OX 50,” “130,” “150” and “200” silicas from Degussa Corp.,Akron, Ohio and CAB-O-SIL M5 and TS-720 silica from Cabot Corp.,Tuscola, Ill.). Organic fillers made from polymeric materials are alsopossible, such as those disclosed in International Publication No.WO09/045752 (Kalgutkar et al.). The compositions may further containfibrous reinforcement and colorants such as dyes, pigments, and pigmentdyes. Examples of suitable fibrous reinforcement include PGAmicrofibrils, collagen microfibrils, and others as described in U.S.Pat. No. 6,183,593 (Narang et al.). Examples of suitable colorants asdescribed in U.S. Pat. No. 5,981,621 (Clark et al.) include1-hydroxy-4-[4-methylphenylamino]-9,10-anthracenedione (FD&C violet No.2); disodium salt of6-hydroxy-5-[(4-sulfophenyl)oxo]-2-naphthalenesulfonic acid (FD&C YellowNo. 6);9-(o-carboxyphenyl)-6-hydroxy-2,4,5,7-tetraiodo-3H-xanthen-3-one,disodium salt, monohydrate (FD&C Red No. 3); and the like.

Discontinuous fibers are also suitable fillers, such as fiberscomprising carbon, ceramic, glass, or combinations thereof. Suitablediscontinuous fibers can have a variety of compositions, such as ceramicfibers. The ceramic fibers can be produced in continuous lengths, whichare chopped or sheared to provide the discontinuous ceramic fibers. Theceramic fibers can be produced from a variety of commercially availableceramic filaments. Examples of filaments useful in forming the ceramicfibers include the ceramic oxide fibers sold under the trademark NEXTEL(3M Company, St. Paul, Minn.). NEXTEL is a continuous filament ceramicoxide fiber having low elongation and shrinkage at operatingtemperatures, and offers good chemical resistance, low thermalconductivity, thermal shock resistance, and low porosity. Specificexamples of NEXTEL fibers include NEXTEL 312, NEXTEL 440, NEXTEL 550,NEXTEL 610 and NEXTEL 720. NEXTEL 312 and NEXTEL 440 are refractoryaluminoborosilicate that includes Al₂O₃, SiO₂ and B₂O₃. NEXTEL 550 andNEXTEL 720 are aluminosilica and NEXTEL 610 is alumina. Duringmanufacture, the NEXTEL filaments are coated with organic sizings orfinishes which serves as aids in textile processing. Sizing can includethe use of starch, oil, wax or other organic ingredients applied to thefilament strand to protect and aid handling. The sizing can be removedfrom the ceramic filaments by heat cleaning the filaments or ceramicfibers as a temperature of 700° C. for one to four hours.

The ceramic fibers can be cut, milled, or chopped so as to providerelatively uniform lengths, which can be accomplished by cuttingcontinuous filaments of the ceramic material in a mechanical shearingoperation or laser cutting operation, among other cutting operations.Given the highly controlled nature of certain cutting operations, thesize distribution of the ceramic fibers is very narrow and allow tocontrol the composite property. The length of the ceramic fiber can bedetermined, for instance, using an optical microscope (Olympus MX61,Tokyo, Japan) fit with a CCD Camera (Olympus DP72, Tokyo, Japan) andanalytic software (Olympus Stream Essentials, Tokyo, Japan). Samples maybe prepared by spreading representative samplings of the ceramic fiberon a glass slide and measuring the lengths of at least 200 ceramicfibers at 10× magnification.

Suitable fibers include for instance ceramic fibers available under thetrade name NEXTEL (available from 3M Company, St. Paul, Minn.), such asNEXTEL 312, 440, 610 and 720. One presently preferred ceramic fibercomprises polycrystalline α-Al₂O₃. Suitable alumina fibers aredescribed, for example, in U.S. Pat. No. 4,954,462 (Wood et al.) andU.S. Pat. No. 5,185,299 (Wood et al.). Exemplary alpha alumina fibersare marketed under the trade designation NEXTEL 610 (3M Company, St.Paul, Minn.). In some embodiments, the alumina fibers arepolycrystalline alpha alumina fibers and comprise, on a theoreticaloxide basis, greater than 99 percent by weight Al₂O₃ and 0.2-0.5 percentby weight SiO₂, based on the total weight of the alumina fibers. Inother embodiments, some desirable polycrystalline, alpha alumina fiberscomprise alpha alumina having an average grain size of less than onemicrometer (or even, in some embodiments, less than 0.5 micrometer). Insome embodiments, polycrystalline, alpha alumina fibers have an averagetensile strength of at least 1.6 GPa (in some embodiments, at least 2.1GPa, or even, at least 2.8 GPa). Suitable aluminosilicate fibers aredescribed, for example, in U.S. Pat. No. 4,047,965 (Karst et al).Exemplary aluminosilicate fibers are marketed under the tradedesignations NEXTEL 440, and NEXTEL 720, by 3M Company (St. Paul,Minn.). Aluminoborosilicate fibers are described, for example, in U.S.Pat. No. 3,795,524 (Sowman). Exemplary aluminoborosilicate fibers aremarketed under the trade designation NEXTEL 312 by 3M Company. Boronnitride fibers can be made, for example, as described in U.S. Pat. No.3,429,722 (Economy) and U.S. Pat. No. 5,780,154 (Okano et al.).

Ceramic fibers can also be formed from other suitable ceramic oxidefilaments. Examples of such ceramic oxide filaments include thoseavailable from Central Glass Fiber Co., Ltd. (e.g., EFH75-01,EFH150-31). Also preferred are aluminoborosilicate glass fibers, whichcontain less than about 2% alkali or are substantially free of alkali(i.e., “E-glass” fibers). E-glass fibers are available from numerouscommercial suppliers.

Examples of useful pigments include, without limitation: white pigments,such as titanium oxide, zinc phosphate, zinc sulfide, zinc oxide andlithopone; red and red-orange pigments, such as iron oxide (maroon, red,light red), iron/chrome oxide, cadmium sulfoselenide and cadmium mercury(maroon, red, orange); ultramarine (blue, pink and violet), chrome-tin(pink) manganese (violet), cobalt (violet); orange, yellow and buffpigments such as barium titanate, cadmium sulfide (yellow), chrome(orange, yellow), molybdate (orange), zinc chromate (yellow), nickeltitanate (yellow), iron oxide (yellow), nickel tungsten titanium, zincferrite and chrome titanate; brown pigments such as iron oxide (buff,brown), manganese/antimony/titanium oxide, manganese titanate, naturalsiennas (umbers), titanium tungsten manganese; blue-green pigments, suchas chrome aluminate (blue), chrome cobalt-alumina (turquoise), iron blue(blue), manganese (blue), chrome and chrome oxide (green) and titaniumgreen; as well as black pigments, such as iron oxide black and carbonblack. Combinations of pigments are generally used to achieve thedesired color tone in the cured composition.

The use of florescent dyes and pigments can also be beneficial inenabling the printed composition to be viewed under black-light. Aparticularly useful hydrocarbon soluble fluorescing dye is2,5-bis(5-tert-butyl-2-benzoxazolyl) 1 thiophene. Fluorescing dyes, suchas rhodamine, may also be bound to cationic polymers and incorporated aspart of the resin.

If desired, the compositions of the disclosure may contain otheradditives such as indicators, accelerators, surfactants, wetting agents,antioxidants, tartaric acid, chelating agents, buffering agents, andother similar ingredients that will be apparent to those skilled in theart. Additionally, medicaments or other therapeutic substances can beoptionally added to the photopolymerizable compositions. Examplesinclude, but are not limited to, fluoride sources, whitening agents,anticaries agents (e.g., xylitol), remineralizing agents (e.g., calciumphosphate compounds and other calcium sources and phosphate sources),enzymes, breath fresheners, anesthetics, clotting agents, acidneutralizers, chemotherapeutic agents, immune response modifiers,thixotropes, polyols, anti-inflammatory agents, antimicrobial agents,antifungal agents, agents for treating xerostomia, desensitizers, andthe like, of the type often used in dental compositions.

Combinations of any of the above additives may also be employed. Theselection and amount of any one such additive can be selected by one ofskill in the art to accomplish the desired result without undueexperimentation.

Photopolymerizable compositions materials herein can also exhibit avariety of desirable properties, non-cured, cured, and as post-curedarticles. A photopolymerizable composition, when non-cured, has aviscosity profile consistent with the requirements and parameters of oneor more additive manufacturing devices (e.g., 3D printing systems). Insome instances, a photopolymerizable composition described herein whennon-cured exhibits a dynamic viscosity of about 0.1-1,000 Pa·s, about0.1-100 Pa·s, or about 1-10 Pa·s using a TA Instruments AR-G2 magneticbearing rheometer using a 40 mm cone and plate measuring system at 40degrees Celsius and at a shear rate of 0.1 l/s, when measured accordingto ASTM D4287, as set forth in the Example Test Method below. In somecases, a photopolymerizable composition described herein when non-curedexhibits a dynamic viscosity of less than about 10 Pa·s, when measuredaccording to modified ASTM D4287.

Articles and Methods

In a second aspect, the present disclosure provides an article. Thearticle comprises a reaction product of a photopolymerizablecomposition, the photopolymerizable composition comprising:

(a) 50 to 90 wt. %, inclusive, of at least one urethane component;

(b) 5 to 50 wt. %, inclusive, of at least one reactive diluent;

(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and

(d) an optional inhibitor in an amount of 0.001 to 1 wt. %, inclusive,if present; based on the total weight of the photopolymerizablecomposition. In many embodiments, the photopolymerizable composition ofthe article is vat polymerized, as discussed in detail below.

The shape of the article is not limited, and may comprise a film or ashaped integral article. For instance, a film may readily be prepared bycasting the photopolymerizable composition according to the firstaspect, then subjecting the cast composition to actinic radiation topolymerize the photopolymerizable composition. In many embodiments, thearticle comprises a shaped integral article, in which more than onevariation in dimension is provided by a single integral article. Forexample, the article can comprise one or more channels, one or moreundercuts, one or more perforations, or combinations thereof. Suchfeatures are typically not possible to provide in an integral articleusing conventional molding methods. In select embodiments, the articlecomprises an orthodontic article. Orthodontic articles are described infurther detail below.

In a third aspect, the present disclosure provides a method of making anarticle. The method comprises:

(i) providing a photopolymerizable composition comprising: (a) 50 to 90wt. %, inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition;

(ii) selectively curing the photopolymerizable composition to form anarticle; and

(iii) optionally curing unpolymerized urethane component and/or reactivediluent remaining after step (ii).

In many embodiments, the photopolymerizable composition is cured usingactinic radiation comprising UV radiation, e-beam radiation, visibleradiation, or a combination thereof. Moreover, the method optionallyfurther comprises postcuring the article using actinic radiation orheat.

In additive manufacturing methods, the method further comprises (iv)repeating steps (i) and (ii) to form multiple layers and create thearticle comprising a three dimensional structure prior to step (iii). Incertain embodiments, the method comprises vat polymerization of thephotopolymerizable composition. When vat polymerization is employed, theradiation may be directed through a wall of a container (e.g., a vat)holding the photopolymerizable composition, such as a side wall or abottom wall.

A photopolymerizable composition described herein in a cured state, insome embodiments, can exhibit one or more desired properties. Aphotopolymerizable composition in a “cured” state can comprise aphotopolymerizable composition that includes a polymerizable componentthat has been at least partially polymerized and/or crosslinked. Forinstance, in some instances, a cured article is at least about 10%polymerized or crosslinked or at least about 30% polymerized orcrosslinked. In some cases, a cured photopolymerizable composition is atleast about 50%, at least about 70%, at least about 80%, or at leastabout 90% polymerized or crosslinked. A cured photopolymerizablecomposition can also be between about 10% and about 99% polymerized orcrosslinked.

The conformability and durability of a cured article made from thephotopolymerizable compositions of the present disclosure can bedetermined in part by standard tensile, modulus, and/or elongationtesting. The photopolymerizable compositions can typically becharacterized by at least one of the following parameters afterhardening. Advantageously, the elongation at break is typically 25% orgreater, 27% or greater, 30% or greater, 32% or greater, 35% or greater,40% or greater, 45% or greater, 50% or greater, 55% or greater, or 60%or greater; and 200% or less, 100% or less, 90% or less, 80% or less, or70% or less. Stated another way, the elongation at break of the curedarticle can range from 25% to 200%. In some embodiments, the elongationat break is at least 30% and no greater than 100%. The ultimate tensilestrength is typically 15 MegaPascals (MPa) or greater, 20 MPa orgreater, 25 MPa or greater, or 30 MPa or greater, and is typically 80MPa or less, each as determined according to ASTM D638-10. While theurethane component has the greatest effect on the elongation at break ofan article, other components of the photopolymerizable composition alsoimpact the elongation at break, e.g., the length of a linear chain orbranch of a reactive diluent tends to be positively correlated to theelongation at break of the final article. The tensile modulus istypically 200 MPa or greater, as determined according to ASTM D638-10.Such elongation properties can be measured, for example, by the methodsoutlined in ASTM D638-10, using test specimen Type V. The mechanicalproperties above are particularly well suited for articles that requireresiliency and flexibility, along with adequate wear strength and lowhygroscopicity.

Photopolymerizable compositions described herein can be mixed by knowntechniques. In some embodiments, for instance, a method for thepreparation of a photopolymerizable composition described hereincomprises the steps of mixing all or substantially all of the componentsof the photopolymerizable composition, heating the mixture, andoptionally filtering the heated mixture. Softening the mixture, in someembodiments, is carried out at a temperature of about 50° C. or in arange from about 50° C. to about 85° C. In some embodiments, aphotopolymerizable composition described herein is produced by placingall or substantially all components of the composition in a reactionvessel and heating the resulting mixture to a temperature ranging fromabout 50° C. to about 85° C. with stirring. The heating and stirring arecontinued until the mixture attains a substantially homogenized state.

Fabricating an Article

Once prepared as set forth above, the photopolymerizable compositions ofthe present disclosure may be used in myriad additive manufacturingprocesses to create a variety of articles, including casting a film asnoted above. A generalized method 100 for creating three-dimensionalarticles is illustrated in FIG. 1. Each step in the method will bediscussed in greater detail below. First, in Step 110 the desiredphotopolymerizable composition (e.g., comprising at least one urethanecomponent, at least one reactive diluent, and a photoinitiator) isprovided and introduced into a reservoir, cartridge, or other suitablecontainer for use by or in an additive manufacturing device. Theadditive manufacturing device selectively cures the photopolymerizablecomposition according to a set of computerized design instructions inStep 120. In Step 130, Step 110 and/or Step 120 is repeated to formmultiple layers to create the article comprising a three dimensionalstructure (e.g., an orthodontic aligner). Optionally uncuredphotopolymerizable composition is removed from the article in Step 140,and further optionally, the article is subjected to additional curing topolymerize remaining uncured photopolymerizable components in thearticle in Step 150.

Methods of printing a three dimensional article or object describedherein can include forming the article from a plurality of layers of aphotopolymerizable composition described herein in a layer-by-layermanner. Further, the layers of a build material composition can bedeposited according to an image of the three dimensional article in acomputer readable format. In some or all embodiments, thephotopolymerizable composition is deposited according to preselectedcomputer aided design (CAD) parameters.

Additionally, it is to be understood that methods of manufacturing a 3Darticle described herein can include so-called “stereolithography/vatpolymerization” 3D printing methods. Other techniques forthree-dimensional manufacturing are known, and may be suitably adaptedto use in the applications described herein. More generally,three-dimensional fabrication techniques continue to become available.All such techniques may be adapted to use with photopolymerizablecompositions described herein, provided they offer compatiblefabrication viscosities and resolutions for the specified articleproperties. Fabrication may be performed using any of the fabricationtechnologies described herein, either alone or in various combinations,using data representing a three-dimensional object, which may bereformatted or otherwise adapted as necessary for a particular printingor other fabrication technology.

It is entirely possible to form a 3D article from a photopolymerizablecomposition described herein using vat polymerization (e.g.,stereolithography). For example, in some cases, a method of printing a3D article comprises retaining a photopolymerizable compositiondescribed herein in a fluid state in a container and selectivelyapplying energy to the photopolymerizable composition in the containerto solidify at least a portion of a fluid layer of thephotopolymerizable composition, thereby forming a hardened layer thatdefines a cross-section of the 3D article. Additionally, a methoddescribed herein can further comprise raising or lowering the hardenedlayer of photopolymerizable composition to provide a new or second fluidlayer of unhardened photopolymerizable composition at the surface of thefluid in the container, followed by again selectively applying energy tothe photopolymerizable composition in the container to solidify at leasta portion of the new or second fluid layer of the photopolymerizablecomposition to form a second solidified layer that defines a secondcross-section of the 3D article. Further, the first and secondcross-sections of the 3D article can be bonded or adhered to one anotherin the z-direction (or build direction corresponding to the direction ofraising or lowering recited above) by the application of the energy forsolidifying the photopolymerizable composition. Moreover, selectivelyapplying energy to the photopolymerizable composition in the containercan comprise applying actinic radiation, such as UV radiation, visibleradiation, or e-beam radiation, having a sufficient energy to cure thephotopolymerizable composition. A method described herein can alsocomprise planarizing a new layer of fluid photopolymerizable compositionprovided by raising or lowering an elevator platform. Such planarizationcan be carried out, in some cases, by utilizing a wiper or roller or arecoater bead. Planarization corrects the thickness of one or morelayers prior to curing the material by evening the dispensed material toremove excess material and create a uniformly smooth exposed or flatup-facing surface on the support platform of the printer.

It is further to be understood that the foregoing process can berepeated a selected number of times to provide the 3D article. Forexample, in some cases, this process can be repeated “n” number oftimes. Further, it is to be understood that one or more steps of amethod described herein, such as a step of selectively applying energyto a layer of photopolymerizable composition, can be carried outaccording to an image of the 3D article in a computer-readable format.Suitable stereolithography printers include the Viper Pro SLA, availablefrom 3D Systems, Rock Hill, S.C. and the Asiga Pico Plus39, availablefrom Asiga USA, Anaheim Hills, Calif.

FIG. 2 shows an exemplary stereolithography apparatus (“SLA”) that maybe used with the photopolymerizable compositions and methods describedherein. In general, the SLA 200 may include a laser 202, optics 204, asteering lens 206, an elevator 208, a platform 210, and a straight edge212, within a vat 214 filled with the photopolymerizable composition. Inoperation, the laser 202 is steered across a surface of thephotopolymerizable composition to cure a cross-section of thephotopolymerizable composition, after which the elevator 208 slightlylowers the platform 210 and another cross section is cured. The straightedge 212 may sweep the surface of the cured composition between layersto smooth and normalize the surface prior to addition of a new layer. Inother embodiments, the vat 214 may be slowly filled with liquid resinwhile an article is drawn, layer by layer, onto the top surface of thephotopolymerizable composition.

A related technology, vat polymerization with Digital Light Processing(“DLP”), also employs a container of curable polymer (e.g.,photopolymerizable composition). However, in a DLP based system, atwo-dimensional cross section is projected onto the curable material tocure the desired section of an entire plane transverse to the projectedbeam at one time. All such curable polymer systems as may be adapted touse with the photopolymerizable compositions described herein areintended to fall within the scope of the term “vat polymerizationsystem” as used herein. In certain embodiments, an apparatus adapted tobe used in a continuous mode may be employed, such as an apparatuscommercially available from Carbon 3D, Inc. (Redwood City, Calif.), forinstance as described in U.S. Pat. Nos. 9,205,601 and 9,360,757 (both toDeSimone et al.).

Referring to FIG. 5, a general schematic is provided of another SLAapparatus that may be used with photopolymerizable compositions andmethods described herein. In general, the apparatus 500 may include alaser 502, optics 504, a steering lens 506, an elevator 508, and aplatform 510, within a vat 514 filled with the photopolymerizablecomposition 519. In operation, the laser 502 is steered through a wall520 (e.g., the floor) of the vat 514 and into the photopolymerizablecomposition to cure a cross-section of the photopolymerizablecomposition 519 to form an article 517, after which the elevator 508slightly raises the platform 510 and another cross section is cured.

More generally, the photopolymerizable composition is typically curedusing actinic radiation, such as UV radiation, e-beam radiation, visibleradiation, or any combination thereof. The skilled practitioner canselect a suitable radiation source and range of wavelengths for aparticular application without undue experimentation.

After the 3D article has been formed, it is typically removed from theadditive manufacturing apparatus and rinsed, (e.g., an ultrasonic, orbubbling, or spray rinse in a solvent, which would dissolve a portion ofthe uncured photopolymerizable composition but not the cured, solidstate article (e.g., green body). Any other conventional method forcleaning the article and removing uncured material at the articlesurface may also be utilized. At this stage, the three-dimensionalarticle typically has sufficient green strength for handling in theremaining optional steps of method 100.

It is expected in certain embodiments of the present disclosure that theformed article obtained in Step 120 will shrink (i.e., reduce in volume)such that the dimensions of the article after (optional) Step 150 willbe smaller than expected. For example, a cured article may shrink lessthan 5% in volume, less than 4%, less than 3%, less than 2%, or evenless than 1% in volume, which is contrast to other compositions thatprovide articles that shrink about 6-8% in volume upon optionalpostcuring. The amount of volume percent shrinkage will not typicallyresult in a significant distortion in the shape of the final object. Itis particularly contemplated, therefore, that dimensions in the digitalrepresentation of the eventual cured article may be scaled according toa global scale factor to compensate for this shrinkage. For example, insome embodiments, at least a portion of the digital articlerepresentation can be at least 101% of the desired size of the printedappliance, in some embodiments at least 102%, in some embodiments atleast 104%, in some embodiments, at least 105%, and in some embodiments,at least 110%.

A global scale factor may be calculated for any given photopolymerizablecomposition formulation by creating a calibration part according toSteps 110 and 120 above. The dimensions of the calibration article canbe measured prior to postcuring.

In general, the three-dimensional article formed by initial additivemanufacturing in Step 120, as discussed above, is not fully cured, bywhich is meant that not all of the photopolymerizable material in thecomposition has polymerized even after rinsing. Some uncuredphotopolymerizable material is typically removed from the surface of theprinted article during a cleaning process (e.g., optional Step 140). Thearticle surface, as well as the bulk article itself, typically stillretains uncured photopolymerizable material, suggesting further cure.Removing residual uncured photopolymerizable composition is particularlyuseful when the article is going to subsequently be postcured, tominimize uncured residual photopolymerizable composition fromundesirably curing directly onto the article.

Further curing can be accomplished by further irradiating with actinicradiation, heating, or both. Exposure to actinic radiation can beaccomplished with any convenient radiation source, generally UVradiation, visible radiation, and/or e-beam radiation, for a timeranging from about 10 to over 60 minutes. Heating is generally carriedout at a temperature in the range of about 75-150° C., for a timeranging from about 10 to over 60 minutes in an inert atmosphere. Socalled post cure ovens, which combine UV radiation and thermal energy,are particularly well suited for use in the postcure process of Step150. In general, postcuring improves the mechanical properties andstability of the three-dimensional article relative to the samethree-dimensional article that is not postcured.

The following describes general methods for creating a clear trayaligner as printed appliance 300. However, other dental and orthodonticarticles can be created using similar techniques and thephotopolymerizable compositions of the present disclosure.Representative examples include, but are not limited to, the removableappliances having occlusal windows described in InternationalApplication Publication No. WO2016/109660 (Raby et al.), the removableappliances with a palatal plate described in US Publication No.2014/0356799 (Cinader et al); and the resilient polymeric arch membersdescribed in International Application Nos. WO2016/148960 andWO2016/149007 (Oda et al.); as well as US Publication No. 2008/0248442(Cinader et al.). Moreover, the photopolymerizable compositions can beused in the creation of indirect bonding trays, such as those describedin International Publication No. WO2015/094842 (Paehl et al.) and USPublication No. 2011/0091832 (Kim, et al.) and other dental articles,including but not limited to crowns, bridges, veneers, inlays, onlays,fillings, and prostheses (e.g., partial or full dentures). Otherorthodontic appliances and devices include, but not limited to,orthodontic brackets, buccal tubes, lingual retainers, orthodonticbands, class II and class III correctors, sleep apnea devices, biteopeners, buttons, cleats, and other attachment devices.

Alternatively, the photopolymerizable compositions can be used in otherindustries, such as aerospace, animation and entertainment, architectureand art, automotive, consumer goods and packaging, education,electronics, hearing aids, sporting goods, jewelry, medical,manufacturing, etc.

Fabricating an Orthodontic Appliance with the PhotopolymerizableCompositions

One particularly interesting implementation of an article is generallydepicted in FIG. 3. The additive manufactured article 300 is a cleartray aligner and is removably positionable over some or all of apatient's teeth. In some embodiments, the appliance 300 is one of aplurality of incremental adjustment appliances. The appliance 300 maycomprise a shell having an inner cavity. The inner cavity is shaped toreceive and resiliently reposition teeth from one tooth arrangement to asuccessive tooth arrangement. The inner cavity may include a pluralityof receptacles, each of which is adapted to connect to and receive arespective tooth of the patient's dental arch. The receptacles arespaced apart from each other along the length of the cavity, althoughadjoining regions of adjacent receptacles can be in communication witheach other. In some embodiments, the shell fits over all teeth presentin the upper jaw or lower jaw. Typically, only certain one(s) of theteeth will be repositioned while others of the teeth will provide a baseor anchor region for holding the dental appliance in place as it appliesthe resilient repositioning force against the tooth or teeth to betreated.

In order to facilitate positioning of the teeth of the patient, at leastone of receptacles may be misaligned as compared to the correspondingtooth of the patient. In this manner, the appliance 300 may beconfigured to apply rotational and/or translational forces to thecorresponding tooth of the patient when the appliance 300 is worn by thepatient. In some particular examples, the appliance 300 may beconfigured to provide only compressive or linear forces. In the same ordifferent examples, the appliance 300 may be configured to applytranslational forces to one or more of the teeth within receptacles.

In some embodiments, the shell of the appliance 300 fits over some orall anterior teeth present in an upper jaw or lower jaw. Typically, onlycertain one(s) of the teeth will be repositioned while others of theteeth will provide a base or anchor region for holding the appliance inplace as it applies the resilient repositioning force against the toothor teeth to be repositioned. An appliance 300 can accordingly bedesigned such that any receptacle is shaped to facilitate retention ofthe tooth in a particular position in order to maintain the currentposition of the tooth.

A method 400 of creating an orthodontic appliance using thephotopolymerizable compositions of the present disclosure can includegeneral steps as outlined in FIG. 4. Individual aspects of the processare discussed in further detail below. The process includes generating atreatment plan for repositioning a patient's teeth. Briefly, a treatmentplan can include obtaining data representing an initial arrangement ofthe patient's teeth (Step 410), which typically includes obtaining animpression or scan of the patient's teeth prior to the onset oftreatment. The treatment plan will also include identifying a final ortarget arrangement of the patient's anterior and posterior teeth asdesired (Step 420), as well as a plurality of planned successive orintermediary tooth arrangements for moving at least the anterior teethalong a treatment path from the initial arrangement toward the selectedfinal or target arrangement (Step 430). One or more appliances can bevirtually designed based on the treatment plan (Step 440), and imagedata representing the appliance designs can exported in STL format, orin any other suitable computer processable format, to an additivemanufacturing device (e.g., a 3D printer system) (Step 450). Anappliance can be manufactured using a photopolymerizable composition ofthe present disclosure retained in the additive manufacturing device(Step 460).

In some embodiments, a (e.g., non-transitory) machine-readable medium isemployed in additive manufacturing of articles according to at leastcertain aspects of the present disclosure. Data is typically stored onthe machine-readable medium. The data represents a three-dimensionalmodel of an article, which can be accessed by at least one computerprocessor interfacing with additive manufacturing equipment (e.g., a 3Dprinter, a manufacturing device, etc.). The data is used to cause theadditive manufacturing equipment to create an article comprising areaction product of a photopolymerizable composition, thephotopolymerizable composition comprising: (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition. In certain embodiments,the article is an orthodontic article. Preferably, the article has anelongation at break of 25% or greater.

Data representing an article may be generated using computer modelingsuch as computer aided design (CAD) data. Image data representing the(e.g., polymeric) article design can be exported in STL format, or inany other suitable computer processable format, to the additivemanufacturing equipment. Scanning methods to scan a three-dimensionalobject may also be employed to create the data representing the article.One exemplary technique for acquiring the data is digital scanning. Anyother suitable scanning technique may be used for scanning an article,including X-ray radiography, laser scanning, computed tomography (CT),magnetic resonance imaging (MRI), and ultrasound imaging. Other possiblescanning methods are described, e.g., in U.S. Patent ApplicationPublication No. 2007/0031791 (Cinader, Jr., et al.). The initial digitaldata set, which may include both raw data from scanning operations anddata representing articles derived from the raw data, can be processedto segment an article design from any surrounding structures (e.g., asupport for the article). In embodiments wherein the article is anorthodontic article, scanning techniques may include, for example,scanning a patient's mouth to customize an orthodontic article for thepatient.

Often, machine-readable media are provided as part of a computingdevice. The computing device may have one or more processors, volatilememory (RAM), a device for reading machine-readable media, andinput/output devices, such as a display, a keyboard, and a pointingdevice. Further, a computing device may also include other software,firmware, or combinations thereof, such as an operating system and otherapplication software. A computing device may be, for example, aworkstation, a laptop, a personal digital assistant (PDA), a server, amainframe or any other general-purpose or application-specific computingdevice. A computing device may read executable software instructionsfrom a computer-readable medium (such as a hard drive, a CD-ROM, or acomputer memory), or may receive instructions from another sourcelogically connected to computer, such as another networked computer.Referring to FIG. 10, a computing device 1000 often includes an internalprocessor 1080, a display 1100 (e.g., a monitor), and one or more inputdevices such as a keyboard 1140 and a mouse 1120. In FIG. 10, an aligner1130 is shown on the display 1100.

Referring to FIG. 6, in certain embodiments, the present disclosureprovides a system 600. The system 600 comprises a display 620 thatdisplays a 3D model 610 of an article (e.g., an aligner 1130 as shown onthe display 1100 of FIG. 10); and one or more processors 630 that, inresponse to the 3D model 610 selected by a user, cause a 3Dprinter/additive manufacturing device 650 to create a physical object ofthe article 660. Often, an input device 640 (e.g., keyboard and/ormouse) is employed with the display 620 and the at least one processor630, particularly for the user to select the 3D model 610. The article660 comprises a reaction product of a photopolymerizable composition,the photopolymerizable composition comprising: (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition.

Referring to FIG. 7, a processor 720 (or more than one processor) is incommunication with each of a machine-readable medium 710 (e.g., anon-transitory medium), a 3D printer/additive manufacturing device 740,and optionally a display 730 for viewing by a user. The 3Dprinter/additive manufacturing device 740 is configured to make one ormore articles 750 based on instructions from the processor 720 providingdata representing a 3D model of the article 750 (e.g., an aligner 1130as shown on the display 1100 of FIG. 10) from the machine-readablemedium 710.

Referring to FIG. 8, for example and without limitation, an additivemanufacturing method comprises retrieving 810, from a (e.g.,non-transitory) machine-readable medium, data representing a 3D model ofan article according to at least one embodiment of the presentdisclosure. The method further includes executing 820, by one or moreprocessors, an additive manufacturing application interfacing with amanufacturing device using the data; and generating 830, by themanufacturing device, a physical object of the article. The additivemanufacturing equipment can selectively cure a photopolymerizablecomposition to form an article. The article comprises a reaction productof a photopolymerizable composition, the photopolymerizable compositioncomprising: (a) 50 to 90 wt. %, inclusive, of at least one urethanecomponent; (b) 5 to 50 wt. %, inclusive, of at least one reactivediluent; (c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and (d) anoptional inhibitor in an amount of 0.001 to 1 wt. %, inclusive, ifpresent; based on the total weight of the photopolymerizablecomposition. One or more various optional post-processing steps 840 maybe undertaken. Typically, remaining unpolymerized photopolymerizablecomponent may be cured. In certain embodiments, the article comprises anorthodontic article. Additionally, referring to FIG. 9, a method ofmaking an article comprises receiving 910, by a manufacturing devicehaving one or more processors, a digital object comprising dataspecifying a plurality of layers of an article; and generating 920, withthe manufacturing device by an additive manufacturing process, thearticle based on the digital object. Again, the article may undergo oneor more steps of post-processing 930.

Select Embodiments of the Disclosure

Embodiment 1 is a photopolymerizable composition. The photopolymerizablecomposition includes (a) 50 to 90 wt. %, inclusive, of at least oneurethane component and (b) 5 to 50 wt. %, inclusive, of at least onereactive diluent. The photopolymerizable composition further includes(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition.

Embodiment 2 is the photopolymerizable composition of embodiment 1,wherein the at least one urethane component is present in an amount of60 to 80 wt. %, inclusive, of the total weight of the photopolymerizablecomposition.

Embodiment 3 is the photopolymerizable composition of embodiment 1 orembodiment 2, wherein the at least one urethane component includes ahigh number average molecular weight (Mn) urethane component having oneor more urethane functionalities in the backbone of the compound and anumber average molecular weight of 1,000 grams per mole (g/mol) orgreater, with the proviso that all branches off the backbone of thecompound, if present, have a Mn of no more than 200 g/mol.

Embodiment 4 is the photopolymerizable composition of embodiment 3,wherein the at least one urethane component includes 80 wt. % or more,85 wt. % or more, 90 wt. % or more, or 95 wt. % or more of the high Mnurethane component.

Embodiment 5 is the photopolymerizable composition of embodiment 3 orembodiment 4, wherein the at least one urethane component furtherincludes a low Mn urethane component having one or more urethanefunctionalities in the backbone of the compound and have either 1) anumber average molecular weight of 100 g/mol or greater and up to butnot including 1,000 g/mol, or 2) a Mn of 100 g/mol or greater and 2,000g/mol or less, with the proviso that a Mn of any one or more linearportions between two reactive groups and/or branches is up to but notincluding 1,000 g/mol.

Embodiment 6 is the photopolymerizable composition of embodiment 5,wherein the at least one urethane component includes 20 wt. % or less,16 wt. % or less, 11 wt. % or less, 9 wt. % or less, or 6 wt. % or lessof the low Mn urethane component.

Embodiment 7 is the photopolymerizable composition of embodiment 5 orembodiment 6, wherein a ratio of the high Mn urethane component to thelow Mn urethane component ranges from 95:5 high Mn urethane component tolow Mn urethane component to 80:20 high Mn urethane component to low Mnurethane component.

Embodiment 8 is the photopolymerizable composition of any of embodiments1 to 7, wherein the at least one urethane component includes a urethane(meth)acrylate, a urethane acrylamide, or combinations thereof, andwherein the at least one urethane component includes a linking groupselected from alkyl, polyalkylene, polyalkylene oxide, aryl,polycarbonate, polyester, polyamide, and combinations thereof.

Embodiment 9 is the photopolymerizable composition of any of embodiments1 to 8, wherein the at least one urethane component includes a urethane(meth)acrylate comprising a polyalkylene oxide linking group, apolyamide linking group, or combinations thereof.

Embodiment 10 is the photopolymerizable composition of any ofembodiments 1 to 9, wherein the at least one reactive diluent has amolecular weight of 200 grams per mole to 400 grams per mole, inclusive.

Embodiment 11 is the photopolymerizable composition of any ofembodiments 1 to 10, wherein the at least one reactive diluent includesa (meth)acrylate, a polyalkylene oxide di(meth)acrylate, an alkane dioldi(meth)acrylate, or combinations thereof.

Embodiment 12 is the photopolymerizable composition of any ofembodiments 1 to 11, wherein the at least one reactive diluent includesa (meth)acrylate.

Embodiment 13 is the photopolymerizable composition of any ofembodiments 1 to 12, wherein the photopolymerizable composition consistsessentially of multifunctional components.

Embodiment 14 is the photopolymerizable composition of any ofembodiments 1 to 13, wherein the photopolymerizable composition is freeof monofunctional components.

Embodiment 15 is the photopolymerizable composition of any ofembodiments 1 to 14, including 25 to 50 wt. %, inclusive, of the atleast one reactive diluent.

Embodiment 16 is the photopolymerizable composition of any ofembodiments 1 to 15, further including 0.01 to 1 wt. %, inclusive, of anabsorption modifier.

Embodiment 17 is the photopolymerizable composition of any ofembodiments 1 to 16, wherein the photopolymerizable composition has aviscosity at a temperature of 40 degrees Celsius of 10 Pa·s or less, asdetermined using a magnetic bearing rheometer using a 40 mm cone andplate measuring system at a shear rate of 0.1 l/s.

Embodiment 18 is the photopolymerizable composition of any ofembodiments 1 to 17, further including at least one filler.

Embodiment 19 is the photopolymerizable composition of any ofembodiments 1 to 18, further including at least one filler selected fromsilica, alumina, zirconia, and discontinuous fibers.

Embodiment 20 is the photopolymerizable composition of embodiment 19,wherein the discontinuous fibers include carbon, ceramic, glass, orcombinations thereof.

Embodiment 21 is an article comprising a reaction product of aphotopolymerizable composition. The photopolymerizable compositionincludes (a) 50 to 90 wt. %, inclusive, of at least one urethanecomponent and (b) 5 to 50 wt. %, inclusive, of at least one reactivediluent. The photopolymerizable composition further includes (c) 0.1 to5 wt. %, inclusive, of a photoinitiator and (d) an optional inhibitor inan amount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition.

Embodiment 22 is the article of embodiment 21, wherein the articlecomprises a plurality of layers.

Embodiment 23 is the article of embodiment 21 or embodiment 22,including a film or a shaped integral article.

Embodiment 24 is the article of any of embodiments 21 to 23, includingan orthodontic article.

Embodiment 25 is the article of any of embodiments 21 to 24, includingone or more channels, one or more undercuts, one or more perforations,or combinations thereof.

Embodiment 26 is the article of any of embodiments 21 to 25, exhibitingan elongation at break of 25% or greater.

Embodiment 27 is the article of any of embodiments 21 to 26, exhibitinga tensile strength of 20 MegaPascals (MPa) or greater, as determinedaccording to ASTM D638-10.

Embodiment 28 is the article of any of embodiments 21 to 27, exhibitinga modulus of 200 MPa or greater, as determined according to ASTMD638-10.

Embodiment 29 is the article of any of embodiments 21 to 28, wherein theat least one urethane component is present in the photopolymerizablecomposition in an amount of 60 to 80 wt. %, inclusive, of the totalweight of the photopolymerizable composition.

Embodiment 30 is the article of any of embodiment 21 to 29, wherein theat least one urethane component includes a high number average molecularweight (Mn) urethane component having one or more urethanefunctionalities in the backbone of the compound and a number averagemolecular weight of 1,000 grams per mole (g/mol) or greater, with theproviso that all branches off the backbone of the compound, if present,have a Mn of no more than 200 g/mol.

Embodiment 31 is the article of embodiment 30, wherein the at least oneurethane component includes 80 wt. % or more, 85 wt. % or more, 90 wt. %or more, or 95 wt. % or more of the high Mn urethane component.

Embodiment 32 is the article of embodiment 30 or embodiment 31, whereinthe at least one urethane component further includes a low Mn urethanecomponent having one or more urethane functionalities in the backbone ofthe compound and have either 1) a number average molecular weight of 100g/mol or greater and up to but not including 1,000 g/mol, or 2) a Mn of100 g/mol or greater and 2,000 g/mol or less, with the proviso that a Mnof any one or more linear portions between two reactive groups and/orbranches is up to but not including 1,000 g/mol.

Embodiment 33 is the article of embodiment 32, wherein the at least oneurethane component includes 20 wt. % or less, 16 wt. % or less, 11 wt. %or less, 9 wt. % or less, or 6 wt. % or less of the low Mn urethanecomponent.

Embodiment 34 is the article of embodiment 32 or embodiment 33, whereina ratio of the high Mn urethane component to the low Mn urethanecomponent ranges from 95:5 high Mn urethane component to low Mn urethanecomponent to 80:20 high Mn urethane component to low Mn urethanecomponent.

Embodiment 35 is the article of any of embodiments 21 to 34, wherein theat least one urethane component includes a urethane (meth)acrylate, aurethane acrylamide, or combinations thereof, and wherein the at leastone urethane component comprises a linking group selected from alkyl,polyalkylene, polyalkylene oxide, aryl, polycarbonate, polyester,polyamide, and combinations thereof.

Embodiment 36 is the article of any of embodiments 21 to 35, wherein theat least one urethane component includes a urethane (meth)acrylatecomprising a polyalkylene oxide linking group, a polyamide linkinggroup, or combinations thereof.

Embodiment 37 is the article of any of embodiments 21 to 36, wherein theat least one urethane component includes two urethane components.

Embodiment 38 is the article of any of embodiments 21 to 37, wherein theat least one reactive diluent has a molecular weight of 200 grams permole to 400 grams per mole, inclusive.

Embodiment 39 is the article of any of embodiments 21 to 38, wherein theat least one reactive diluent includes a (meth)acrylate, a polyalkyleneoxide di(meth)acrylate, an alkane diol di(meth)acrylate, or combinationsthereof.

Embodiment 40 is the article of any of embodiments 21 to 39, wherein theat least one reactive diluent includes a (meth)acrylate.

Embodiment 41 is the article of any of embodiments 21 to 40, wherein thephotopolymerizable composition consists essentially of multifunctionalcomponents.

Embodiment 42 is the article of any of embodiments 21 to 41, wherein thephotopolymerizable composition is free of monofunctional components.

Embodiment 43 is the article of any of embodiments 21 to 42, wherein thephotopolymerizable composition includes 25 to 50 wt. %, inclusive, ofthe at least one reactive diluent.

Embodiment 44 is the article of any of embodiments 21 to 43, wherein thephotopolymerizable composition further includes 0.01 to 1 wt. %,inclusive, of an absorption modifier.

Embodiment 45 is the article of any of embodiments 21 to 44, wherein thephotopolymerizable composition has a viscosity at a temperature of 40degrees Celsius of 10 Pa·s or less, as determined using a magneticbearing rheometer using a 40 mm cone and plate measuring system at ashear rate of 0.1 l/s.

Embodiment 46 is the article of any of embodiments 21 to 45, furtherincluding at least one filler.

Embodiment 47 is the article of any of embodiments 21 to 46, furtherincluding at least one filler selected from silica, alumina, zirconia,and discontinuous fibers.

Embodiment 48 is the article of embodiment 47, wherein the discontinuousfibers include carbon, ceramic, glass, or combinations thereof.

Embodiment 49 is a method of making an article. The method includes (i)providing a photopolymerizable composition and (ii) selectively curingthe photopolymerizable composition to form an article. The methodoptionally also includes (iii) curing unpolymerized urethane componentand/or reactive diluent remaining after step (ii). Thephotopolymerizable composition includes (a) 50 to 90 wt. %, inclusive,of at least one urethane component; (b) 5 to 50 wt. %, inclusive, of atleast one reactive diluent; (c) 0.1 to 5 wt. %, inclusive, of aphotoinitiator; and (d) an optional inhibitor in an amount of 0.001 to 1wt. %, inclusive, if present; based on the total weight of thephotopolymerizable composition.

Embodiment 50 is the method of embodiment 49, further including (iv)repeating steps (i) and (ii) to form multiple layers and create thearticle having a three dimensional structure prior to step (iii).

Embodiment 51 is the method of embodiment 49 or embodiment 50, whereinthe photopolymerizable composition is cured using actinic radiationincluding UV radiation, e-beam radiation, visible radiation, or acombination thereof.

Embodiment 52 is the method of embodiment 51, wherein the radiation isdirected through a wall of a container holding the photopolymerizablecomposition.

Embodiment 53 is the method of any of embodiments 49 to 51, wherein thephotopolymerizable composition is cured through a floor of a containerholding the photopolymerizable composition.

Embodiment 54 is the method of any of embodiments 49 to 53, furtherincluding postcuring the article using actinic radiation or heat.

Embodiment 55 is the method of any of embodiments 49 to 54, wherein themethod includes vat polymerization of the photopolymerizablecomposition.

Embodiment 56 is the method of any of embodiments 49 to 55, wherein thearticle includes a film or a shaped integral article.

Embodiment 57 is the method of any of embodiments 49 to 56, wherein thearticle includes an orthodontic article.

Embodiment 58 is the method of any of embodiments 49 to 57, wherein thearticle includes one or more channels, one or more undercuts, one ormore perforations, or combinations thereof.

Embodiment 59 is the method of any of embodiments 49 to 58, wherein thearticle exhibits an elongation at break of 25% or greater.

Embodiment 60 is the method of any of embodiments 49 to 59, wherein thearticle exhibits a tensile strength of 20 MegaPascals (MPa) or greater,as determined according to ASTM D638-10.

Embodiment 61 is the method of any of embodiments 49 to 60, wherein thearticle exhibits a modulus of 200 MPa or greater, as determinedaccording to ASTM D638-10.

Embodiment 62 is the method of any of embodiments 49 to 61, wherein theat least one urethane component is present in the photopolymerizablecomposition in an amount of 60 to 80 wt. %, inclusive, of the totalweight of the photopolymerizable composition.

Embodiment 63 is the method of any of any of embodiment 49 to 62,wherein the at least one urethane component includes a high numberaverage molecular weight (Mn) urethane component having one or moreurethane functionalities in the backbone of the compound and a numberaverage molecular weight of 1,000 grams per mole (g/mol) or greater,with the proviso that all branches off the backbone of the compound, ifpresent, have a Mn of no more than 200 g/mol.

Embodiment 64 is the method of embodiment 63, wherein the at least oneurethane component includes 80 wt. % or more, 85 wt. % or more, 90 wt. %or more, or 95 wt. % or more of the high Mn urethane component.

Embodiment 65 is the method of embodiment 63 or embodiment 64, whereinthe at least one urethane component further includes a low Mn urethanecomponent having one or more urethane functionalities in the backbone ofthe compound and have either 1) a number average molecular weight of 100g/mol or greater and up to but not including 1,000 g/mol, or 2) a Mn of100 g/mol or greater and 2,000 g/mol or less, with the proviso that a Mnof any one or more linear portions between two reactive groups and/orbranches is up to but not including 1,000 g/mol.

Embodiment 66 is the method of embodiment 65, wherein the at least oneurethane component includes 20 wt. % or less, 16 wt. % or less, 11 wt. %or less, 9 wt. % or less, or 6 wt. % or less of the low Mn urethanecomponent.

Embodiment 67 is the method of embodiment 63 or embodiment 66, wherein aratio of the high Mn urethane component to the low Mn urethane componentranges from 95:5 high Mn urethane component to low Mn urethane componentto 80:20 high Mn urethane component to low Mn urethane component.

Embodiment 68 is the method of any of embodiments 49 to 67, wherein theat least one urethane component includes a urethane (meth)acrylate, aurethane acrylamide, or combinations thereof, and wherein the at leastone urethane component comprises a linking group selected from alkyl,polyalkylene, polyalkylene oxide, aryl, polycarbonate, polyester,polyamide, and combinations thereof.

Embodiment 69 is the method of any of embodiments 49 to 68, wherein theat least one urethane component includes a urethane (meth)acrylatecomprising a polyalkylene oxide linking group, a polyamide linkinggroup, or combinations thereof.

Embodiment 70 is the method of any of embodiments 49 to 69, wherein theat least one reactive diluent has a molecular weight of 200 grams permole to 400 grams per mole, inclusive.

Embodiment 71 is the method of any of embodiments 49 to 70, wherein theat least one reactive diluent includes a (meth)acrylate, a polyalkyleneoxide di(meth)acrylate, an alkane diol di(meth)acrylate, or combinationsthereof.

Embodiment 72 is the method of any of embodiments 49 to 71, wherein theat least one reactive diluent includes a (meth)acrylate.

Embodiment 73 is the method of any of embodiments 49 to 72, wherein thephotopolymerizable composition consists essentially of multifunctionalcomponents.

Embodiment 74 is the method of any of embodiments 49 to 73, wherein thephotopolymerizable composition is free of monofunctional components.

Embodiment 75 is the method of any of embodiments 49 to 74, wherein thephotopolymerizable composition includes 25 to 50 wt. %, inclusive, ofthe at least one reactive diluent.

Embodiment 76 is the method of any of embodiments 49 to 75, wherein thephotopolymerizable composition further includes 0.01 to 1 wt. %,inclusive, of an absorption modifier.

Embodiment 77 is the method of any of embodiments 49 to 76, wherein thephotopolymerizable composition has a viscosity at a temperature of 40degrees Celsius of 10 Pa·s or less, as determined using a magneticbearing rheometer using a 40 mm cone and plate measuring system at ashear rate of 0.1 l/s.

Embodiment 78 is the method of any of embodiments 49 to 77, furtherincluding at least one filler.

Embodiment 79 is the method of any of embodiments 49 to 78, furtherincluding at least one filler selected from silica, alumina, zirconia,and discontinuous fibers.

Embodiment 80 is the method of embodiment 79, wherein the discontinuousfibers include carbon, ceramic, glass, or combinations thereof.

Embodiment 81 is a non-transitory machine readable medium. Thenon-transitory machine readable medium has data representing athree-dimensional model of an article, when accessed by one or moreprocessors interfacing with a 3D printer, causes the 3D printer tocreate an article. The article includes a reaction product of aphotopolymerizable composition including (a) 50 to 90 wt. %, inclusive,of at least one urethane component and (b) 5 to 50 wt. %, inclusive, ofat least one reactive diluent. The photopolymerizable compositionfurther includes (c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and(d) an optional inhibitor in an amount of 0.001 to 1 wt. %, inclusive,if present; based on the total weight of the photopolymerizablecomposition. The article exhibits an elongation at break of 25% orgreater.

Embodiment 82 is a method. The method includes retrieving, from anon-transitory machine readable medium, data representing a 3D model ofan article; executing, by one or more processors, a 3D printingapplication interfacing with a manufacturing device using the data; andgenerating, by the manufacturing device, a physical object of thearticle. The article includes a reaction product of a photopolymerizablecomposition including (a) 50 to 90 wt. %, inclusive, of at least oneurethane component and (b) 5 to 50 wt. %, inclusive, of at least onereactive diluent. The photopolymerizable composition further includes(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition. The articleexhibits an elongation at break of 25% or greater.

Embodiment 83 is an article generated using the method of embodiment 82.

Embodiment 84 is the article of embodiment 82, wherein the articleincludes an orthodontic article.

Embodiment 85 is a method. The method includes receiving, by amanufacturing device having one or more processors, a digital objectcomprising data specifying a plurality of layers of an article; andgenerating, with the manufacturing device by an additive manufacturingprocess, the article based on the digital object. The article includes areaction product of a photopolymerizable composition including (a) 50 to90 wt. %, inclusive, of at least one urethane component and (b) 5 to 50wt. %, inclusive, of at least one reactive diluent. Thephotopolymerizable composition further includes (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition. The article exhibits anelongation at break of 25% or greater.

Embodiment 86 is the method of embodiment 85, wherein the additivemanufacturing equipment selectively cures a photopolymerizablecomposition to form an article. The photopolymerizable compositionincludes (a) 50 to 90 wt. %, inclusive, of at least one urethanecomponent and (b) 5 to 50 wt. %, inclusive, of at least one reactivediluent. The photopolymerizable composition further includes (c) 0.1 to5 wt. %, inclusive, of a photoinitiator; and (d) an optional inhibitorin an amount of 0.001 to 1 wt. %, inclusive, if present; based on thetotal weight of the photopolymerizable composition. The article exhibitsan elongation at break of 25% or greater.

Embodiment 87 is the method of embodiment 86, further including curingunpolymerized urethane component and/or reactive diluent, remaining inthe article.

Embodiment 88 is the method of embodiment 86 or embodiment 87, whereinthe article includes an orthodontic article.

Embodiment 89 is a system. The system includes a display that displays a3D model of an article; and one or more processors that, in response tothe 3D model selected by a user, cause a 3D printer to create a physicalobject of an article. The article includes a reaction product of aphotopolymerizable composition including (a) 50 to 90 wt. %, inclusive,of at least one urethane component and (b) 5 to 50 wt. %, inclusive, ofat least one reactive diluent. The photopolymerizable compositionfurther includes (c) 0.1 to 5 wt. %, inclusive, of a photoinitiator and(d) an optional inhibitor in an amount of 0.001 to 1 wt. %, inclusive,if present; based on the total weight of the photopolymerizablecomposition. The article exhibits an elongation at break of 25% orgreater.

EXAMPLES

Objects and advantages of this disclosure are further illustrated by thefollowing examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this disclosure.

Testing of Exemplary Compositions

The materials used in the following examples are summarized in Table 1.

TABLE 1 Summary of materials. Functionality/ Linear MW between 2reactive groups Molecular (if different Material Description Sourceweight (Mn) from MW) High Mn Urethane Components: Exothane 108 UrethaneEsstech Inc, (Essington, 1000-1500* 2 (meth)acrylate PA) oligomerExothane 10 Urethane Esstech Inc, (Essington, >1000**     2(meth)acrylate PA) oligomer CN9007 Urethane Sartomer (Exton, PA) — 2(meth)acrylate oligomer Low Mn Urethane Components: DESMA Urethane 3MCompany (St. Paul, 1233***  2/822 (meth)acrylate MN) UDMA UrethaneEsstech Inc, (Essington,  470.5*** 2 Dimethacrylate PA) Additives: BHT2,6-Di-tert-butyl-4- Fluka Analytical (St. — — methyl-phenol Louis, MO)TINOPAL OB 2,5- BASF, Wyandotte, MI — — Thiophenediylbis(5-ten-butyl-1,3- benzoxazole) (optical brightener) IRGAGURE 2,4,6- BASF(Wyandotte, MI) — — TPO Trimethylbenzoyldiphenyl- phosphine oxide(photoinitiator) Reactive Diluents: TEGDMA TriethyleneglycolSigma-Aldrich (St.  286.3*** 2 dimethacrylate Louis, MO) D-ZethacrylateEthoxylated 3M Company (St. Paul,  367.5*** 2 bisphenol A MN)dimethacrylate; polymerizable methacrylate BisEMA6 Ethoxylated (6)Sartomer (Exton, PA)  395.5*** 2 bisphenol A dimethacrylate DDDMA1,12-Dodecanediol Sartomer (Exton, PA)  338.5*** 2 dimethacrylate HDDMA1,6-Hexanediol Sartomer (Exton, PA)  254.3*** 2 dimethacrylate Unlessotherwise noted, all printed Examples were printed on an AsigaPicoPlus39, a vat polymerization 3D printer available from Asiga USA,Anaheim Hills, CA. *measured using matrix assisted laser depositionionization mass spectrometry (MALDI) **estimated from structure deducedfrom nuclear magnetic resonance (NMR) ***as labelled

Preparation of Formulated Resins

Resins were prepared according to the formulations listed in Table 2below, by roller mixing the components overnight to ensure thoroughmixing.

TABLE 2 Resin Formulations (wt. %) Exothane Exothane Reactive Amt ofReactive IRGACURE TINOPAL Example 108 10 CN9007 UDMA DESMA DiluentDiluent TPO OB BHT CE-1 33.3 — — — 33.3 TEGDMA 33.3 1 0.1 0.1 CE-2 46.15— — — 7.69 TEGDMA 46.15 1 0.1 0.1 CE-3 — — — 80 — TEGDMA 20 0.5 0.050.05 CE-4 74.07 — — — 22.22 TEGDMA 3.7 0.5 0.05 0.05 E-1 80 — — — —TEGDMA 20 1 0.1 0.1 E-2 70 — — — — TEGDMA 30 1 0.1 0.1 E-3 70 — — — 5TEGDMA 25 0.5 0.05 0.05 E-4 60 — — — 5 D-Zethacrylate 35 1 0.1 0.1 E-565.1 — — — 5.8 BisEMA6 29.1 0.5 0.025 0.025 E-6 — 70 — 5 TEGDMA 25 0.50.025 0.025 E-7 35 35 — — 5 TEGDMA 25 0.5 0.025 0.025 E-8 75 — — — 12.5TEGDMA 12.5 1 0.1 0.1

Viscosity of the Resins

Absolute (e.g., dynamic) viscosities of the example resins were measuredusing a TA Instruments AR-G2 magnetic bearing rheometer using a 40 mmcone and plate measuring system at 40° C. at a shear rate of 0.1 l/s.Two replicates were measured and the average value was reported as theviscosity, in Pa·s, in Table 3 below.

TABLE 3 Viscosities of Example resins in Pa · s. Sample ID Viscosity (Pa· s) CE-1 0.69 CE-2 0.14 CE-3 — CE-4 16.35 E-1 3.36 E-2 0.91 E-3 1.85E-4 5.96 E-5 7.8 E-6 0.09 E-7 1.57 E-8 6.28Physical Properties of Polymers from Cast Resin Formulations

The Example 1 (E-1) formulation shown in Table 1 was mixed in a glassjar. The E-1 mixture was placed on a rolling mixer to make a homogenousmixture. The mixture was degassed and speed mixed in THINKY planetarymixer (Thinky Corporation, Tokyo, Japan), at 2000 rpm for 90 secondsunder vacuum. The mixture was then poured in a silicone dogbone mold(Type V mold, ASTM D638-10). The filled mold was placed between twoglass plates and cured in a broad spectrum UV chamber (Dymax LightCuring Systems Model 2000 Flood) for 5 minutes. The sample was demoldedand cured for another 5 minutes in the chamber, according to ASTMD638-10. These dogbones were tested on an Insight MTS with 5 kN loadcell at the rate of 5 mm/minute. Five replicate samples were tested, andthe average and standard deviation are reported. The tensile strength,tensile modulus and elongation at break of the samples were determinedaccording to ASTM D638-10 and shown in Table 4 below.

Subsequent examples, E-2-E-8 and CE-1-CE-4, were made by the same method(the formulations for these examples are summarized in Table 2 above)and tested. The test results of the cast samples are summarized in Table4 below.

TABLE 4 Tensile strength (MPa), Tensile Modulus (MPa) and Elongation atbreak (%) of Cast Formulations. Tensile Tensile Elongation at StrengthModulus Break (Std Sample ID (Std Dev) (Std Dev) Dev) CE-1 43.7 (0.6)1423 (326.5) 21.1 (5.5) CE-2 40.3 (2.1) 2293.7 (813.5)  19.7 (2.8) CE-384.3 (3.1) 3935.3 (1531.4)  5.1 (1.0) CE-4 28.7 (0.6) 387.3 (56.1)  54.6(7)   E-1 26.9 (3.6) 535.9 (58.1)  42.0 (7.7) E-2 32.7 (2.5) 762.3(96.5)  34.4 (4.6) E-3   31 (1.7) 729.7 (201.1) 39.5 (4.6) E-4 33 (2)1411.7 (566.0)  27.2 (3.2) E-5   29 (4.6)   651 (170.7) 40.2 (6.7) E-635.7 (2.9) 697.7 (158)   33.8 (2.4) E-7 40.2 (2.2) 1367.2 (437.8)  29.8(1.9) E-8 28.3 (3.1) 533.7 (197)   45.2 (4.8)

Additive Manufacturing of Formulated Resins

The formulations of E-3 and E-7 resins were photopolymerized on theAsiga Pico 2 printer with a LED light source of 385 nm and ˜23 mW/cm² ofpower. Tensile test bars of Type V according to ASTM D638-10 weremanufactured. The resin bath of the printer was heated to 35-40° C.before photopolymerization to reduce the viscosity to be able tomanufacture the tensile test bars. The following settings were used:Slice thickness=50 μm, Burn-In Layers=3, Separation Velocity=10 mm/s,Slides per Layer=1, Burn-In Exposure Time=15.0 s, Normal ExposureTime=3.1 s. The test bars were then cleaned in isopropanol to removeunreacted resin. The test bars were then post-cured under fusion lampsfor 90 minutes on each side. The post-cured dogbones were tested on anInsight MTS with 5 kN load cell at the rate of 5 mm/minute. Fivereplicate samples were tested, and the average and standard deviationare reported. The tensile strength of the samples was determinedaccording to ASTM D638-10 and shown in Table 5 below.

TABLE 5 Tensile strength (MPa), Tensile Modulus (MPa) and Elongation atbreak (%) of 3D printed Formulations Tensile Tensile Elongation atStrength Modulus Break (Std Sample ID (Std Dev) (Std Dev) Dev) E-3 26.8(3.3) 586.9 (47.1) 39.5 (7.9) E-7 29.4 (0.7) 946.3 (30.8) 30.6 (2.4)Additive Manufacturing of Aligner Article from the Formulated Resin

The formulation of E-3 was photopolymerized on the Asiga Pico 2 HDprinter with a LED light source of 385 nm and ˜16 mW/cm² of power. AnSTL file of the aligner was loaded into the software and supportstructures were generated. The resin bath of the printer was heated to35-40° C. before photopolymerization to reduce the viscosity to be ableto manufacture the article. The following settings were used: Slicethickness=50 μm, Burn-In Layers=3, Separation Velocity=10 mm/s, Slidesper Layer=1, Burn-In Exposure Time=15.0 s, Normal Exposure Time=3.1 s.The photopolymerized aligners were then cleaned in isopropanol to removeunreacted resin and then post-cured under fusion lamps for 90 minutes oneach side. The photopolymerized aligners fit the models, showingprecision of the additive manufacture part. The aligners also hadacceptable strength and flexibility.

All of the patents and patent applications mentioned above are herebyexpressly incorporated by reference. The embodiments described above areillustrative of the present invention and other constructions are alsopossible. Accordingly, the present invention should not be deemedlimited to the embodiments described in detail above and shown in theaccompanying drawings, but instead only by a fair scope of the claimsthat follow along with their equivalents.

1. A photopolymerizable composition comprising: (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent, wherein the at least onereactive diluent has a molecular weight of 400 grams per mole or less,is free of any urethane functional groups, and comprises a methacrylate;(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition, wherein thephotopolymerizable composition has a viscosity at a temperature of 40degrees Celsius of 10 Pa·s or less, as determined using a magneticbearing rheometer using a 40 mm cone and plate measuring system at ashear rate of 0.1 l/s, and wherein the photopolymerizable composition isfree of monofunctional components.
 2. The photopolymerizable compositionof claim 1, wherein the at least one urethane oligomer comprises aurethane (meth)acrylate, a urethane acrylamide, or combinations thereof,and wherein the at least one urethane component comprises a linkinggroup selected from alkyl, polyalkylene, polyalkylene oxide, aryl,polycarbonate, polyester, polyamide, and combinations thereof.
 3. Thephotopolymerizable composition of claim 1, wherein the at least oneurethane comprises a high Mn urethane component and a low Mn urethanecomponent, wherein a ratio of the high Mn urethane component to the lowMn urethane component ranges from 95:5 high Mn urethane component to lowMn urethane component to 80:20 high Mn urethane component to low Mnurethane component.
 4. The photopolymerizable composition of claim 1,wherein the at least one reactive diluent comprises a molecular weightof 200 grams per mole to 400 grams per mole, inclusive.
 5. Thephotopolymerizable composition of claim 1, wherein the at least onereactive diluent comprises one or more of ethoxylated bisphenol Adimethacrylate, tetraethylene glycol dimethacrylate, triethyleneglycoldimethacrylate, 1,3-propanediol dimethacrylate, 1,2,4-butanetrioltrimethacrylate, pentaerythritol tetramethacrylate,trishydroxyethyl-isocyanurate trimethacrylate, or a bis-methacrylate ofa polyethylene glycol.
 6. (canceled)
 7. An article comprising a reactionproduct of a photopolymerizable composition, the photopolymerizablecomposition comprising: (a) 50 to 90 wt. %, inclusive, of at least oneurethane component; (b) 5 to 50 wt. %, inclusive, of at least onereactive diluent, wherein the at least one reactive diluent has amolecular weight of 400 grams per mole or less, is free of any urethanefunctional groups, and comprises a methacrylate; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition, wherein thephotopolymerizable composition is free of monofunctional components, andwherein the article exhibits an elongation at break of 25% or greater.8. The article of claim 7, wherein the article comprises an orthodonticarticle.
 9. The article of claim 7, comprising one or more channels, oneor more undercuts, one or more perforations, or combinations thereof.10. The article of claim 7, comprising an elongation at break of 30% orgreater.
 11. The article of claim 7, comprising a tensile strength of 20MegaPascals (MPa) or greater, as determined according to ASTM D638-10.12. The article of claim 7, comprising a modulus of 200 MPa or greater,as determined according to ASTM D638-10.
 13. A method of making anarticle, the method comprising: (i) providing a photopolymerizablecomposition comprising: (a) 50 to 90 wt. %, inclusive, of at least oneurethane component; (b) 5 to 50 wt. %, inclusive, of at least onereactive diluent, wherein the at least one reactive diluent has amolecular weight of 400 grams per mole or less, is free of any urethanefunctional groups, and comprises a methacrylate; (c) 0.1 to 5 wt. %,inclusive, of a photoinitiator; and (d) an optional inhibitor in anamount of 0.001 to 1 wt. %, inclusive, if present; based on the totalweight of the photopolymerizable composition, wherein thephotopolymerizable composition is free of monofunctional components;(ii) selectively curing the photopolymerizable composition to form anarticle; and (iii) optionally curing unpolymerized urethane componentand/or reactive diluent remaining after step (ii), wherein the articleexhibits an elongation at break of 25% or greater.
 14. The method ofclaim 13, further comprising (iv) repeating steps (i) and (ii) to formmultiple layers and create the article comprising a three dimensionalstructure prior to step (iii).
 15. A non-transitory machine readablemedium having data representing a three-dimensional model of an article,when accessed by one or more processors interfacing with a 3D printer,causes the 3D printer to create an article, the article comprising: areaction product of a photopolymerizable composition, thephotopolymerizable composition comprising: (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent, wherein the at least onereactive diluent has a molecular weight of 400 grams per mole or less,is free of any urethane functional groups, and comprises a methacrylate;(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition, wherein thephotopolymerizable composition is free of monofunctional components, andwherein the article exhibits an elongation at break of 25% or greater.16. A method comprising: retrieving, from a non-transitory machinereadable medium, data representing a 3D model of an article, the articlecomprising: a reaction product of a photopolymerizable composition, thephotopolymerizable composition comprising: (a) 50 to 90 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent, wherein the at least onereactive diluent has a molecular weight of 400 grams per mole or less,is free of any urethane functional groups, and comprises a methacrylate;(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition, wherein thephotopolymerizable composition is free of monofunctional components;executing, by one or more processors, a 3D printing applicationinterfacing with a manufacturing device using the data; and generating,by the manufacturing device, a physical object of the article, whereinthe article exhibits an elongation at break of 25% or greater.
 17. Amethod comprising: receiving, by a manufacturing device having one ormore processors, a digital object comprising data specifying a pluralityof layers of an article, the article comprising: a reaction product of aphotopolymerizable composition, the photopolymerizable compositioncomprising: (a) 50 to 90 wt. %, inclusive, of at least one urethanecomponent; (b) 5 to 50 wt. %, inclusive, of at least one reactivediluent, wherein the at least one reactive diluent has a molecularweight of 400 grams per mole or less, is free of any urethane functionalgroups, and comprises a methacrylate; (c) 0.1 to 5 wt. %, inclusive, ofa photoinitiator; and (d) an optional inhibitor in an amount of 0.001 to1 wt. %, inclusive, if present; based on the total weight of thephotopolymerizable composition, wherein the photopolymerizablecomposition is free of monofunctional components; and generating, withthe manufacturing device by an additive manufacturing process, thearticle based on the digital object, wherein the article exhibits anelongation at break of 25% or greater.
 18. A system comprising: adisplay that displays a 3D model of an article; and one or moreprocessors that, in response to the 3D model selected by a user, cause a3D printer to create a physical object of an article, the articlecomprising: a reaction product of a photopolymerizable composition, thephotopolymerizable composition comprising: (a) 50 to 80 wt. %,inclusive, of at least one urethane component; (b) 5 to 50 wt. %,inclusive, of at least one reactive diluent, wherein the at least onereactive diluent has a molecular weight of 400 grams per mole or less,is free of any urethane functional groups, and comprises a methacrylate;(c) 0.1 to 5 wt. %, inclusive, of a photoinitiator; and (d) an optionalinhibitor in an amount of 0.001 to 1 wt. %, inclusive, if present; basedon the total weight of the photopolymerizable composition, wherein thephotopolymerizable composition is free of monofunctional components, andwherein the article exhibits an elongation at break of 25% or greater.